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Test for array support by shell
The 2019 Stack Overflow Developer Survey Results Are InHow can I safely get the version of ksh?set -A command not running in LinuxBash: minus one to the sub string split by separator$#array vs $#array[@]Shell script: Text files to arrayrotate element of array in shell scriptone-dimensional array in shell not working for indexes greater than 08How to pass array to bash shell script?Error command test shell linuxarray as value for tar --excludeShell scripting help text file into arrayArray inside an Array: Different syntax for Array in bashgrep for multiple elements of an array
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Is there a concise way of testing for array support by the local Bourne-like shell at command line ?
This is always possible:
$ arr=(0 1 2 3);if [ "$arr[2]" != 2 ];then echo "No array support";fi
or testing for $SHELL
and shell version:
$ eval $(echo "$SHELL --version") | grep version
and then reading the man page, assuming I have access to it. (Even there, writing from /bin/bash
, I am assuming that all Bourne-like shells admit the long option --version
, when that breaks for ksh for instance.)
I am looking for a simple test that could be unattended and incorporated in a Usage section at beginning of script or even before calling it.
shell-script shell array
|
show 4 more comments
Is there a concise way of testing for array support by the local Bourne-like shell at command line ?
This is always possible:
$ arr=(0 1 2 3);if [ "$arr[2]" != 2 ];then echo "No array support";fi
or testing for $SHELL
and shell version:
$ eval $(echo "$SHELL --version") | grep version
and then reading the man page, assuming I have access to it. (Even there, writing from /bin/bash
, I am assuming that all Bourne-like shells admit the long option --version
, when that breaks for ksh for instance.)
I am looking for a simple test that could be unattended and incorporated in a Usage section at beginning of script or even before calling it.
shell-script shell array
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
2
csh
is not a bourne shell.tcsh
isn't one either (it'scsh
with some bugs fixed)
– cas
Oct 23 '15 at 10:42
1
Note that$SHELL
is the prefered shell of the user, like$EDITOR
is his preferred text editor. It has little to do with the currently running shell.
– Stéphane Chazelas
Oct 23 '15 at 13:59
1
eval
uating the output of$SHELL --version
as shell code doesn't make sense.
– Stéphane Chazelas
Oct 23 '15 at 14:00
|
show 4 more comments
Is there a concise way of testing for array support by the local Bourne-like shell at command line ?
This is always possible:
$ arr=(0 1 2 3);if [ "$arr[2]" != 2 ];then echo "No array support";fi
or testing for $SHELL
and shell version:
$ eval $(echo "$SHELL --version") | grep version
and then reading the man page, assuming I have access to it. (Even there, writing from /bin/bash
, I am assuming that all Bourne-like shells admit the long option --version
, when that breaks for ksh for instance.)
I am looking for a simple test that could be unattended and incorporated in a Usage section at beginning of script or even before calling it.
shell-script shell array
Is there a concise way of testing for array support by the local Bourne-like shell at command line ?
This is always possible:
$ arr=(0 1 2 3);if [ "$arr[2]" != 2 ];then echo "No array support";fi
or testing for $SHELL
and shell version:
$ eval $(echo "$SHELL --version") | grep version
and then reading the man page, assuming I have access to it. (Even there, writing from /bin/bash
, I am assuming that all Bourne-like shells admit the long option --version
, when that breaks for ksh for instance.)
I am looking for a simple test that could be unattended and incorporated in a Usage section at beginning of script or even before calling it.
shell-script shell array
shell-script shell array
edited yesterday
codeforester
405418
405418
asked Oct 23 '15 at 8:40
CbhiheCbhihe
4291619
4291619
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
2
csh
is not a bourne shell.tcsh
isn't one either (it'scsh
with some bugs fixed)
– cas
Oct 23 '15 at 10:42
1
Note that$SHELL
is the prefered shell of the user, like$EDITOR
is his preferred text editor. It has little to do with the currently running shell.
– Stéphane Chazelas
Oct 23 '15 at 13:59
1
eval
uating the output of$SHELL --version
as shell code doesn't make sense.
– Stéphane Chazelas
Oct 23 '15 at 14:00
|
show 4 more comments
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
2
csh
is not a bourne shell.tcsh
isn't one either (it'scsh
with some bugs fixed)
– cas
Oct 23 '15 at 10:42
1
Note that$SHELL
is the prefered shell of the user, like$EDITOR
is his preferred text editor. It has little to do with the currently running shell.
– Stéphane Chazelas
Oct 23 '15 at 13:59
1
eval
uating the output of$SHELL --version
as shell code doesn't make sense.
– Stéphane Chazelas
Oct 23 '15 at 14:00
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
2
2
csh
is not a bourne shell. tcsh
isn't one either (it's csh
with some bugs fixed)– cas
Oct 23 '15 at 10:42
csh
is not a bourne shell. tcsh
isn't one either (it's csh
with some bugs fixed)– cas
Oct 23 '15 at 10:42
1
1
Note that
$SHELL
is the prefered shell of the user, like $EDITOR
is his preferred text editor. It has little to do with the currently running shell.– Stéphane Chazelas
Oct 23 '15 at 13:59
Note that
$SHELL
is the prefered shell of the user, like $EDITOR
is his preferred text editor. It has little to do with the currently running shell.– Stéphane Chazelas
Oct 23 '15 at 13:59
1
1
eval
uating the output of $SHELL --version
as shell code doesn't make sense.– Stéphane Chazelas
Oct 23 '15 at 14:00
eval
uating the output of $SHELL --version
as shell code doesn't make sense.– Stéphane Chazelas
Oct 23 '15 at 14:00
|
show 4 more comments
2 Answers
2
active
oldest
votes
Assuming you want to restrict to Bourne-like shells (many other shells like csh
, tcsh
, rc
, es
or fish
support arrays but writing a script compatible at the same time to Bourne-like shells and those is tricky and generally pointless as they are interpreters for completely different and incompatible languages), note that there are significant differences between implementations.
The Bourne like shells that support arrays are:
ksh88
(that's the first one implementing arrays, ksh88 is still found asksh
on most traditional commercial Unices where it's also the basis forsh
)- arrays are one-dimensional
- Arrays are defined as
set -A array foo bar
orset -A array -- "$var" ...
if you can't guarantee that$var
won't start with a-
or+
. - Array indices start at
0
. - Individual array elements are assigned as
a[1]=value
. - arrays are sparse. That is
a[5]=foo
will work even ifa[0,1,2,3,4]
are not set and will leave them unset. $a[5]
to access the element of indice 5 (not necessarily the 6th element if the array is sparse). The5
there can be any arithmetic expression.- array size and subscript is limited (to 4096).
$#a[@]
is the number of assigned element in the array (not the greatest assigned indice).- there is no way to know the list of assigned subscripts (other than testing the 4096 elements individually with
[[ -n "$a[i]+set" ]]
). $a
is the same as$a[0]
. That is arrays somehow extend scalar variables by giving them extra values.
pdksh
and derivatives (that's the basis for theksh
and sometimessh
of several BSDs and was the only opensource ksh implementation before ksh93 source was freed):Mostly like
ksh88
but note:- Some old implementations didn't support
set -A array -- foo bar
, (the--
wasn't needed there). $#a[@]
is one plus the indice of the greatest assigned indice. (a[1000]=1; echo "$#a[@]"
outputs 1001 even though the array has only one element.- in newer versions, array size is no longer limited (other than by the size of integers).
- recent versions of
mksh
have a few extra operators inspired frombash
,ksh93
orzsh
like assignments a laa=(x y)
,a+=(z)
,$!a[@]
to get the list of assigned indices.
- Some old implementations didn't support
zsh
.zsh
arrays are generally better designed and take the best ofksh
andcsh
arrays. They are similar toksh
but with significant differences:- indices start at 1, not 0 (except in
ksh
emulation), that's consistent with the Bourne array (the position parameters $@, whichzsh
also exposes as its $argv array) andcsh
arrays. - they are a separate type from normal/scalar variables. Operators apply differently to them and like you'd generally expect.
$a
is not the same as$a[0]
but expands to the non-empty elements of the array ("$a[@]"
for all the elements like inksh
). - they are normal arrays, not sparse arrays.
a[5]=1
works but assigns all the elements from 1 to 4 the empty string if they were not assigned. So$#a[@]
(same as$#a
which in ksh is the size of the element of indice 0) is the number of elements in the array and the greatest assigned indice. - associative arrays are supported.
- a great numbers of operators to work with arrays is supported, too big to list here.
- arrays defined as
a=(x y)
.set -A a x y
also works, butset -A a -- x y
is not supported unless in ksh emulation (the--
is not needed in zsh emulation).
- indices start at 1, not 0 (except in
ksh93
. (here describing latest versions).ksh93
, long considered experimental can now be found in more and more systems now that it has been released as FOSS. For instance, it's the/bin/sh
(where it replaced the Bourne shell,/usr/xpg4/bin/sh
, the POSIX shell is still based onksh88
) andksh
ofSolaris 11
. Its arrays extend and enhance ksh88's.a=(x y)
can be used to define an array, but sincea=(...)
is also used to define compound variables (a=(foo=bar bar=baz)
),a=()
is ambiguous and declares a compound variable, not an array.- arrays are multi-dimensional (
a=((0 1) (0 2))
) and array elements can also be compound variables (a=((a b) (c=d d=f)); echo "$a[1].c"
). - A
a=([2]=foo [5]=bar)
syntax can be used to define sparse arrays at once. - Size limitations lifted.
- Not to the extent of
zsh
, but great number of operators supported as well to manipulate arrays. "$!a[@]"
to retrieve the list of array indices.- associative arrays also supported as a separate type.
bash
.bash
is the shell of the GNU project. It's used assh
on recent versions of OS/X and some GNU/Linux distributions.bash
arrays mostly emulateksh88
ones with some features ofksh93
andzsh
.a=(x y)
supported.set -A a x y
not supported.a=()
creates an empty array (no compound variables inbash
)."$!a[@]"
for the list of indices.a=([foo]=bar)
syntax supported as well as a few others fromksh93
andzsh
.- recent
bash
versions also support associative arrays as a separate type.
yash
. It's a relatively recent, clean, multi-byte aware POSIX sh implementation. Not in wide use. Its arrays are another clean API similar tozsh
- arrays are not sparse
- defined (and declared) with
a=(var value)
- elements inserted, deleted or modified with the
array
builtin array -s a 5 value
to modify the 5th element would fail if that element was not assigned beforehand.- the number of elements in the array is
$a[#]
,$#a[@]
being the size of the elements as a list. - arrays are a separate type. You need
a=("$a")
to redefine a scalar variable as an array before you can add or modify elements. - arrays are not supported when invoked as
sh
.
So, from that you can see that detecting for array support, which you could do with:
if (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "$a[1]" ]'
) > /dev/null 2>&1
then
array_supported=true
else
array_supported=false
fi
is not enough to be able to use those arrays. You'd need to define wrapper commands to assign arrays as a whole and individual elements, and make sure you don't attempt to create sparse arrays.
Like
unset a
array_elements() eval "REPLY="$#$1[@]"";
if (set -A a -- a) 2> /dev/null; then
set -A a -- a b
case $a[0]$a[1] in
--) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=0;;
a) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=1;;
--a) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
ab) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
esac
elif (eval 'a[5]=x') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element() eval "$1[$2]=$3";
first_indice=0
elif (eval 'a=(x) && array -s a 1 y && [ "$a[1]" = y ]') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element()
eval "
$1=($$1+"$$1[@]"'")
while [ "$(($2))" -ge "$'"$1"'[#]" ]; do
array -i "$1" "$2" ""
done'
array -s -- "$1" "$((1+$2))" "$3"
array_elements() eval "REPLY=$$1[#]";
first_indice=1
else
echo >&2 "Array not supported"
fi
And then you access array elements with "$a[$first_indice+n]"
, the whole list with "$a[@]"
and use the wrapper functions (array_elements
, set_array
, set_array_element
) to get the number of elements of an array (in $REPLY
), set the array as a whole or assign individual elements.
Probably not worth the effort. I'd use perl
or limit to the Bourne/POSIX shell array: "$@"
.
If the intent is to have some file to be sourced by the interactive shell of a user to define functions that internally use arrays, here are a few more notes that may be useful.
You can configure zsh
arrays to be more like ksh
arrays in local scopes (in functions or anonymous functions).
myfunction()
[ -z "$ZSH_VERSION" ]
You can also emulate ksh
(improve compatibility with ksh
for arrays and several other areas) with:
myfunction() emulate -L ksh
# ksh code more likely to work here
With that in mind and you're willing to drop support for yash
and ksh88
and older versions of pdksh
derivatives, and as long as you don't try to create sparse arrays, you should be able to consistently use:
a[0]=foo
a=(foo bar)
(but nota=()
)$a[#]
,"$a[@]"
,"$a[0]"
in those functions that have the emulate -L ksh
, while the zsh
user still using his/her arrays normally the zsh way.
add a comment |
You can use eval
to try the array syntax:
is_array_support() (
eval 'a=(1)'
) >/dev/null 2>&1
if is_array_support; then
echo support
else
echo not
fi
2
ksh88
supports arrays but nota=()
. Inksh93
,a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.
– Stéphane Chazelas
Oct 23 '15 at 10:13
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Inyash
, you don't doa[5]=1
butarray -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable inksh93
made me surprise, would you mind giving me part of documentation about it. I add1
to the array to make it work.
– cuonglm
Oct 23 '15 at 10:35
|
show 1 more comment
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2 Answers
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2 Answers
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Assuming you want to restrict to Bourne-like shells (many other shells like csh
, tcsh
, rc
, es
or fish
support arrays but writing a script compatible at the same time to Bourne-like shells and those is tricky and generally pointless as they are interpreters for completely different and incompatible languages), note that there are significant differences between implementations.
The Bourne like shells that support arrays are:
ksh88
(that's the first one implementing arrays, ksh88 is still found asksh
on most traditional commercial Unices where it's also the basis forsh
)- arrays are one-dimensional
- Arrays are defined as
set -A array foo bar
orset -A array -- "$var" ...
if you can't guarantee that$var
won't start with a-
or+
. - Array indices start at
0
. - Individual array elements are assigned as
a[1]=value
. - arrays are sparse. That is
a[5]=foo
will work even ifa[0,1,2,3,4]
are not set and will leave them unset. $a[5]
to access the element of indice 5 (not necessarily the 6th element if the array is sparse). The5
there can be any arithmetic expression.- array size and subscript is limited (to 4096).
$#a[@]
is the number of assigned element in the array (not the greatest assigned indice).- there is no way to know the list of assigned subscripts (other than testing the 4096 elements individually with
[[ -n "$a[i]+set" ]]
). $a
is the same as$a[0]
. That is arrays somehow extend scalar variables by giving them extra values.
pdksh
and derivatives (that's the basis for theksh
and sometimessh
of several BSDs and was the only opensource ksh implementation before ksh93 source was freed):Mostly like
ksh88
but note:- Some old implementations didn't support
set -A array -- foo bar
, (the--
wasn't needed there). $#a[@]
is one plus the indice of the greatest assigned indice. (a[1000]=1; echo "$#a[@]"
outputs 1001 even though the array has only one element.- in newer versions, array size is no longer limited (other than by the size of integers).
- recent versions of
mksh
have a few extra operators inspired frombash
,ksh93
orzsh
like assignments a laa=(x y)
,a+=(z)
,$!a[@]
to get the list of assigned indices.
- Some old implementations didn't support
zsh
.zsh
arrays are generally better designed and take the best ofksh
andcsh
arrays. They are similar toksh
but with significant differences:- indices start at 1, not 0 (except in
ksh
emulation), that's consistent with the Bourne array (the position parameters $@, whichzsh
also exposes as its $argv array) andcsh
arrays. - they are a separate type from normal/scalar variables. Operators apply differently to them and like you'd generally expect.
$a
is not the same as$a[0]
but expands to the non-empty elements of the array ("$a[@]"
for all the elements like inksh
). - they are normal arrays, not sparse arrays.
a[5]=1
works but assigns all the elements from 1 to 4 the empty string if they were not assigned. So$#a[@]
(same as$#a
which in ksh is the size of the element of indice 0) is the number of elements in the array and the greatest assigned indice. - associative arrays are supported.
- a great numbers of operators to work with arrays is supported, too big to list here.
- arrays defined as
a=(x y)
.set -A a x y
also works, butset -A a -- x y
is not supported unless in ksh emulation (the--
is not needed in zsh emulation).
- indices start at 1, not 0 (except in
ksh93
. (here describing latest versions).ksh93
, long considered experimental can now be found in more and more systems now that it has been released as FOSS. For instance, it's the/bin/sh
(where it replaced the Bourne shell,/usr/xpg4/bin/sh
, the POSIX shell is still based onksh88
) andksh
ofSolaris 11
. Its arrays extend and enhance ksh88's.a=(x y)
can be used to define an array, but sincea=(...)
is also used to define compound variables (a=(foo=bar bar=baz)
),a=()
is ambiguous and declares a compound variable, not an array.- arrays are multi-dimensional (
a=((0 1) (0 2))
) and array elements can also be compound variables (a=((a b) (c=d d=f)); echo "$a[1].c"
). - A
a=([2]=foo [5]=bar)
syntax can be used to define sparse arrays at once. - Size limitations lifted.
- Not to the extent of
zsh
, but great number of operators supported as well to manipulate arrays. "$!a[@]"
to retrieve the list of array indices.- associative arrays also supported as a separate type.
bash
.bash
is the shell of the GNU project. It's used assh
on recent versions of OS/X and some GNU/Linux distributions.bash
arrays mostly emulateksh88
ones with some features ofksh93
andzsh
.a=(x y)
supported.set -A a x y
not supported.a=()
creates an empty array (no compound variables inbash
)."$!a[@]"
for the list of indices.a=([foo]=bar)
syntax supported as well as a few others fromksh93
andzsh
.- recent
bash
versions also support associative arrays as a separate type.
yash
. It's a relatively recent, clean, multi-byte aware POSIX sh implementation. Not in wide use. Its arrays are another clean API similar tozsh
- arrays are not sparse
- defined (and declared) with
a=(var value)
- elements inserted, deleted or modified with the
array
builtin array -s a 5 value
to modify the 5th element would fail if that element was not assigned beforehand.- the number of elements in the array is
$a[#]
,$#a[@]
being the size of the elements as a list. - arrays are a separate type. You need
a=("$a")
to redefine a scalar variable as an array before you can add or modify elements. - arrays are not supported when invoked as
sh
.
So, from that you can see that detecting for array support, which you could do with:
if (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "$a[1]" ]'
) > /dev/null 2>&1
then
array_supported=true
else
array_supported=false
fi
is not enough to be able to use those arrays. You'd need to define wrapper commands to assign arrays as a whole and individual elements, and make sure you don't attempt to create sparse arrays.
Like
unset a
array_elements() eval "REPLY="$#$1[@]"";
if (set -A a -- a) 2> /dev/null; then
set -A a -- a b
case $a[0]$a[1] in
--) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=0;;
a) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=1;;
--a) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
ab) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
esac
elif (eval 'a[5]=x') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element() eval "$1[$2]=$3";
first_indice=0
elif (eval 'a=(x) && array -s a 1 y && [ "$a[1]" = y ]') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element()
eval "
$1=($$1+"$$1[@]"'")
while [ "$(($2))" -ge "$'"$1"'[#]" ]; do
array -i "$1" "$2" ""
done'
array -s -- "$1" "$((1+$2))" "$3"
array_elements() eval "REPLY=$$1[#]";
first_indice=1
else
echo >&2 "Array not supported"
fi
And then you access array elements with "$a[$first_indice+n]"
, the whole list with "$a[@]"
and use the wrapper functions (array_elements
, set_array
, set_array_element
) to get the number of elements of an array (in $REPLY
), set the array as a whole or assign individual elements.
Probably not worth the effort. I'd use perl
or limit to the Bourne/POSIX shell array: "$@"
.
If the intent is to have some file to be sourced by the interactive shell of a user to define functions that internally use arrays, here are a few more notes that may be useful.
You can configure zsh
arrays to be more like ksh
arrays in local scopes (in functions or anonymous functions).
myfunction()
[ -z "$ZSH_VERSION" ]
You can also emulate ksh
(improve compatibility with ksh
for arrays and several other areas) with:
myfunction() emulate -L ksh
# ksh code more likely to work here
With that in mind and you're willing to drop support for yash
and ksh88
and older versions of pdksh
derivatives, and as long as you don't try to create sparse arrays, you should be able to consistently use:
a[0]=foo
a=(foo bar)
(but nota=()
)$a[#]
,"$a[@]"
,"$a[0]"
in those functions that have the emulate -L ksh
, while the zsh
user still using his/her arrays normally the zsh way.
add a comment |
Assuming you want to restrict to Bourne-like shells (many other shells like csh
, tcsh
, rc
, es
or fish
support arrays but writing a script compatible at the same time to Bourne-like shells and those is tricky and generally pointless as they are interpreters for completely different and incompatible languages), note that there are significant differences between implementations.
The Bourne like shells that support arrays are:
ksh88
(that's the first one implementing arrays, ksh88 is still found asksh
on most traditional commercial Unices where it's also the basis forsh
)- arrays are one-dimensional
- Arrays are defined as
set -A array foo bar
orset -A array -- "$var" ...
if you can't guarantee that$var
won't start with a-
or+
. - Array indices start at
0
. - Individual array elements are assigned as
a[1]=value
. - arrays are sparse. That is
a[5]=foo
will work even ifa[0,1,2,3,4]
are not set and will leave them unset. $a[5]
to access the element of indice 5 (not necessarily the 6th element if the array is sparse). The5
there can be any arithmetic expression.- array size and subscript is limited (to 4096).
$#a[@]
is the number of assigned element in the array (not the greatest assigned indice).- there is no way to know the list of assigned subscripts (other than testing the 4096 elements individually with
[[ -n "$a[i]+set" ]]
). $a
is the same as$a[0]
. That is arrays somehow extend scalar variables by giving them extra values.
pdksh
and derivatives (that's the basis for theksh
and sometimessh
of several BSDs and was the only opensource ksh implementation before ksh93 source was freed):Mostly like
ksh88
but note:- Some old implementations didn't support
set -A array -- foo bar
, (the--
wasn't needed there). $#a[@]
is one plus the indice of the greatest assigned indice. (a[1000]=1; echo "$#a[@]"
outputs 1001 even though the array has only one element.- in newer versions, array size is no longer limited (other than by the size of integers).
- recent versions of
mksh
have a few extra operators inspired frombash
,ksh93
orzsh
like assignments a laa=(x y)
,a+=(z)
,$!a[@]
to get the list of assigned indices.
- Some old implementations didn't support
zsh
.zsh
arrays are generally better designed and take the best ofksh
andcsh
arrays. They are similar toksh
but with significant differences:- indices start at 1, not 0 (except in
ksh
emulation), that's consistent with the Bourne array (the position parameters $@, whichzsh
also exposes as its $argv array) andcsh
arrays. - they are a separate type from normal/scalar variables. Operators apply differently to them and like you'd generally expect.
$a
is not the same as$a[0]
but expands to the non-empty elements of the array ("$a[@]"
for all the elements like inksh
). - they are normal arrays, not sparse arrays.
a[5]=1
works but assigns all the elements from 1 to 4 the empty string if they were not assigned. So$#a[@]
(same as$#a
which in ksh is the size of the element of indice 0) is the number of elements in the array and the greatest assigned indice. - associative arrays are supported.
- a great numbers of operators to work with arrays is supported, too big to list here.
- arrays defined as
a=(x y)
.set -A a x y
also works, butset -A a -- x y
is not supported unless in ksh emulation (the--
is not needed in zsh emulation).
- indices start at 1, not 0 (except in
ksh93
. (here describing latest versions).ksh93
, long considered experimental can now be found in more and more systems now that it has been released as FOSS. For instance, it's the/bin/sh
(where it replaced the Bourne shell,/usr/xpg4/bin/sh
, the POSIX shell is still based onksh88
) andksh
ofSolaris 11
. Its arrays extend and enhance ksh88's.a=(x y)
can be used to define an array, but sincea=(...)
is also used to define compound variables (a=(foo=bar bar=baz)
),a=()
is ambiguous and declares a compound variable, not an array.- arrays are multi-dimensional (
a=((0 1) (0 2))
) and array elements can also be compound variables (a=((a b) (c=d d=f)); echo "$a[1].c"
). - A
a=([2]=foo [5]=bar)
syntax can be used to define sparse arrays at once. - Size limitations lifted.
- Not to the extent of
zsh
, but great number of operators supported as well to manipulate arrays. "$!a[@]"
to retrieve the list of array indices.- associative arrays also supported as a separate type.
bash
.bash
is the shell of the GNU project. It's used assh
on recent versions of OS/X and some GNU/Linux distributions.bash
arrays mostly emulateksh88
ones with some features ofksh93
andzsh
.a=(x y)
supported.set -A a x y
not supported.a=()
creates an empty array (no compound variables inbash
)."$!a[@]"
for the list of indices.a=([foo]=bar)
syntax supported as well as a few others fromksh93
andzsh
.- recent
bash
versions also support associative arrays as a separate type.
yash
. It's a relatively recent, clean, multi-byte aware POSIX sh implementation. Not in wide use. Its arrays are another clean API similar tozsh
- arrays are not sparse
- defined (and declared) with
a=(var value)
- elements inserted, deleted or modified with the
array
builtin array -s a 5 value
to modify the 5th element would fail if that element was not assigned beforehand.- the number of elements in the array is
$a[#]
,$#a[@]
being the size of the elements as a list. - arrays are a separate type. You need
a=("$a")
to redefine a scalar variable as an array before you can add or modify elements. - arrays are not supported when invoked as
sh
.
So, from that you can see that detecting for array support, which you could do with:
if (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "$a[1]" ]'
) > /dev/null 2>&1
then
array_supported=true
else
array_supported=false
fi
is not enough to be able to use those arrays. You'd need to define wrapper commands to assign arrays as a whole and individual elements, and make sure you don't attempt to create sparse arrays.
Like
unset a
array_elements() eval "REPLY="$#$1[@]"";
if (set -A a -- a) 2> /dev/null; then
set -A a -- a b
case $a[0]$a[1] in
--) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=0;;
a) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=1;;
--a) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
ab) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
esac
elif (eval 'a[5]=x') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element() eval "$1[$2]=$3";
first_indice=0
elif (eval 'a=(x) && array -s a 1 y && [ "$a[1]" = y ]') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element()
eval "
$1=($$1+"$$1[@]"'")
while [ "$(($2))" -ge "$'"$1"'[#]" ]; do
array -i "$1" "$2" ""
done'
array -s -- "$1" "$((1+$2))" "$3"
array_elements() eval "REPLY=$$1[#]";
first_indice=1
else
echo >&2 "Array not supported"
fi
And then you access array elements with "$a[$first_indice+n]"
, the whole list with "$a[@]"
and use the wrapper functions (array_elements
, set_array
, set_array_element
) to get the number of elements of an array (in $REPLY
), set the array as a whole or assign individual elements.
Probably not worth the effort. I'd use perl
or limit to the Bourne/POSIX shell array: "$@"
.
If the intent is to have some file to be sourced by the interactive shell of a user to define functions that internally use arrays, here are a few more notes that may be useful.
You can configure zsh
arrays to be more like ksh
arrays in local scopes (in functions or anonymous functions).
myfunction()
[ -z "$ZSH_VERSION" ]
You can also emulate ksh
(improve compatibility with ksh
for arrays and several other areas) with:
myfunction() emulate -L ksh
# ksh code more likely to work here
With that in mind and you're willing to drop support for yash
and ksh88
and older versions of pdksh
derivatives, and as long as you don't try to create sparse arrays, you should be able to consistently use:
a[0]=foo
a=(foo bar)
(but nota=()
)$a[#]
,"$a[@]"
,"$a[0]"
in those functions that have the emulate -L ksh
, while the zsh
user still using his/her arrays normally the zsh way.
add a comment |
Assuming you want to restrict to Bourne-like shells (many other shells like csh
, tcsh
, rc
, es
or fish
support arrays but writing a script compatible at the same time to Bourne-like shells and those is tricky and generally pointless as they are interpreters for completely different and incompatible languages), note that there are significant differences between implementations.
The Bourne like shells that support arrays are:
ksh88
(that's the first one implementing arrays, ksh88 is still found asksh
on most traditional commercial Unices where it's also the basis forsh
)- arrays are one-dimensional
- Arrays are defined as
set -A array foo bar
orset -A array -- "$var" ...
if you can't guarantee that$var
won't start with a-
or+
. - Array indices start at
0
. - Individual array elements are assigned as
a[1]=value
. - arrays are sparse. That is
a[5]=foo
will work even ifa[0,1,2,3,4]
are not set and will leave them unset. $a[5]
to access the element of indice 5 (not necessarily the 6th element if the array is sparse). The5
there can be any arithmetic expression.- array size and subscript is limited (to 4096).
$#a[@]
is the number of assigned element in the array (not the greatest assigned indice).- there is no way to know the list of assigned subscripts (other than testing the 4096 elements individually with
[[ -n "$a[i]+set" ]]
). $a
is the same as$a[0]
. That is arrays somehow extend scalar variables by giving them extra values.
pdksh
and derivatives (that's the basis for theksh
and sometimessh
of several BSDs and was the only opensource ksh implementation before ksh93 source was freed):Mostly like
ksh88
but note:- Some old implementations didn't support
set -A array -- foo bar
, (the--
wasn't needed there). $#a[@]
is one plus the indice of the greatest assigned indice. (a[1000]=1; echo "$#a[@]"
outputs 1001 even though the array has only one element.- in newer versions, array size is no longer limited (other than by the size of integers).
- recent versions of
mksh
have a few extra operators inspired frombash
,ksh93
orzsh
like assignments a laa=(x y)
,a+=(z)
,$!a[@]
to get the list of assigned indices.
- Some old implementations didn't support
zsh
.zsh
arrays are generally better designed and take the best ofksh
andcsh
arrays. They are similar toksh
but with significant differences:- indices start at 1, not 0 (except in
ksh
emulation), that's consistent with the Bourne array (the position parameters $@, whichzsh
also exposes as its $argv array) andcsh
arrays. - they are a separate type from normal/scalar variables. Operators apply differently to them and like you'd generally expect.
$a
is not the same as$a[0]
but expands to the non-empty elements of the array ("$a[@]"
for all the elements like inksh
). - they are normal arrays, not sparse arrays.
a[5]=1
works but assigns all the elements from 1 to 4 the empty string if they were not assigned. So$#a[@]
(same as$#a
which in ksh is the size of the element of indice 0) is the number of elements in the array and the greatest assigned indice. - associative arrays are supported.
- a great numbers of operators to work with arrays is supported, too big to list here.
- arrays defined as
a=(x y)
.set -A a x y
also works, butset -A a -- x y
is not supported unless in ksh emulation (the--
is not needed in zsh emulation).
- indices start at 1, not 0 (except in
ksh93
. (here describing latest versions).ksh93
, long considered experimental can now be found in more and more systems now that it has been released as FOSS. For instance, it's the/bin/sh
(where it replaced the Bourne shell,/usr/xpg4/bin/sh
, the POSIX shell is still based onksh88
) andksh
ofSolaris 11
. Its arrays extend and enhance ksh88's.a=(x y)
can be used to define an array, but sincea=(...)
is also used to define compound variables (a=(foo=bar bar=baz)
),a=()
is ambiguous and declares a compound variable, not an array.- arrays are multi-dimensional (
a=((0 1) (0 2))
) and array elements can also be compound variables (a=((a b) (c=d d=f)); echo "$a[1].c"
). - A
a=([2]=foo [5]=bar)
syntax can be used to define sparse arrays at once. - Size limitations lifted.
- Not to the extent of
zsh
, but great number of operators supported as well to manipulate arrays. "$!a[@]"
to retrieve the list of array indices.- associative arrays also supported as a separate type.
bash
.bash
is the shell of the GNU project. It's used assh
on recent versions of OS/X and some GNU/Linux distributions.bash
arrays mostly emulateksh88
ones with some features ofksh93
andzsh
.a=(x y)
supported.set -A a x y
not supported.a=()
creates an empty array (no compound variables inbash
)."$!a[@]"
for the list of indices.a=([foo]=bar)
syntax supported as well as a few others fromksh93
andzsh
.- recent
bash
versions also support associative arrays as a separate type.
yash
. It's a relatively recent, clean, multi-byte aware POSIX sh implementation. Not in wide use. Its arrays are another clean API similar tozsh
- arrays are not sparse
- defined (and declared) with
a=(var value)
- elements inserted, deleted or modified with the
array
builtin array -s a 5 value
to modify the 5th element would fail if that element was not assigned beforehand.- the number of elements in the array is
$a[#]
,$#a[@]
being the size of the elements as a list. - arrays are a separate type. You need
a=("$a")
to redefine a scalar variable as an array before you can add or modify elements. - arrays are not supported when invoked as
sh
.
So, from that you can see that detecting for array support, which you could do with:
if (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "$a[1]" ]'
) > /dev/null 2>&1
then
array_supported=true
else
array_supported=false
fi
is not enough to be able to use those arrays. You'd need to define wrapper commands to assign arrays as a whole and individual elements, and make sure you don't attempt to create sparse arrays.
Like
unset a
array_elements() eval "REPLY="$#$1[@]"";
if (set -A a -- a) 2> /dev/null; then
set -A a -- a b
case $a[0]$a[1] in
--) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=0;;
a) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=1;;
--a) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
ab) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
esac
elif (eval 'a[5]=x') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element() eval "$1[$2]=$3";
first_indice=0
elif (eval 'a=(x) && array -s a 1 y && [ "$a[1]" = y ]') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element()
eval "
$1=($$1+"$$1[@]"'")
while [ "$(($2))" -ge "$'"$1"'[#]" ]; do
array -i "$1" "$2" ""
done'
array -s -- "$1" "$((1+$2))" "$3"
array_elements() eval "REPLY=$$1[#]";
first_indice=1
else
echo >&2 "Array not supported"
fi
And then you access array elements with "$a[$first_indice+n]"
, the whole list with "$a[@]"
and use the wrapper functions (array_elements
, set_array
, set_array_element
) to get the number of elements of an array (in $REPLY
), set the array as a whole or assign individual elements.
Probably not worth the effort. I'd use perl
or limit to the Bourne/POSIX shell array: "$@"
.
If the intent is to have some file to be sourced by the interactive shell of a user to define functions that internally use arrays, here are a few more notes that may be useful.
You can configure zsh
arrays to be more like ksh
arrays in local scopes (in functions or anonymous functions).
myfunction()
[ -z "$ZSH_VERSION" ]
You can also emulate ksh
(improve compatibility with ksh
for arrays and several other areas) with:
myfunction() emulate -L ksh
# ksh code more likely to work here
With that in mind and you're willing to drop support for yash
and ksh88
and older versions of pdksh
derivatives, and as long as you don't try to create sparse arrays, you should be able to consistently use:
a[0]=foo
a=(foo bar)
(but nota=()
)$a[#]
,"$a[@]"
,"$a[0]"
in those functions that have the emulate -L ksh
, while the zsh
user still using his/her arrays normally the zsh way.
Assuming you want to restrict to Bourne-like shells (many other shells like csh
, tcsh
, rc
, es
or fish
support arrays but writing a script compatible at the same time to Bourne-like shells and those is tricky and generally pointless as they are interpreters for completely different and incompatible languages), note that there are significant differences between implementations.
The Bourne like shells that support arrays are:
ksh88
(that's the first one implementing arrays, ksh88 is still found asksh
on most traditional commercial Unices where it's also the basis forsh
)- arrays are one-dimensional
- Arrays are defined as
set -A array foo bar
orset -A array -- "$var" ...
if you can't guarantee that$var
won't start with a-
or+
. - Array indices start at
0
. - Individual array elements are assigned as
a[1]=value
. - arrays are sparse. That is
a[5]=foo
will work even ifa[0,1,2,3,4]
are not set and will leave them unset. $a[5]
to access the element of indice 5 (not necessarily the 6th element if the array is sparse). The5
there can be any arithmetic expression.- array size and subscript is limited (to 4096).
$#a[@]
is the number of assigned element in the array (not the greatest assigned indice).- there is no way to know the list of assigned subscripts (other than testing the 4096 elements individually with
[[ -n "$a[i]+set" ]]
). $a
is the same as$a[0]
. That is arrays somehow extend scalar variables by giving them extra values.
pdksh
and derivatives (that's the basis for theksh
and sometimessh
of several BSDs and was the only opensource ksh implementation before ksh93 source was freed):Mostly like
ksh88
but note:- Some old implementations didn't support
set -A array -- foo bar
, (the--
wasn't needed there). $#a[@]
is one plus the indice of the greatest assigned indice. (a[1000]=1; echo "$#a[@]"
outputs 1001 even though the array has only one element.- in newer versions, array size is no longer limited (other than by the size of integers).
- recent versions of
mksh
have a few extra operators inspired frombash
,ksh93
orzsh
like assignments a laa=(x y)
,a+=(z)
,$!a[@]
to get the list of assigned indices.
- Some old implementations didn't support
zsh
.zsh
arrays are generally better designed and take the best ofksh
andcsh
arrays. They are similar toksh
but with significant differences:- indices start at 1, not 0 (except in
ksh
emulation), that's consistent with the Bourne array (the position parameters $@, whichzsh
also exposes as its $argv array) andcsh
arrays. - they are a separate type from normal/scalar variables. Operators apply differently to them and like you'd generally expect.
$a
is not the same as$a[0]
but expands to the non-empty elements of the array ("$a[@]"
for all the elements like inksh
). - they are normal arrays, not sparse arrays.
a[5]=1
works but assigns all the elements from 1 to 4 the empty string if they were not assigned. So$#a[@]
(same as$#a
which in ksh is the size of the element of indice 0) is the number of elements in the array and the greatest assigned indice. - associative arrays are supported.
- a great numbers of operators to work with arrays is supported, too big to list here.
- arrays defined as
a=(x y)
.set -A a x y
also works, butset -A a -- x y
is not supported unless in ksh emulation (the--
is not needed in zsh emulation).
- indices start at 1, not 0 (except in
ksh93
. (here describing latest versions).ksh93
, long considered experimental can now be found in more and more systems now that it has been released as FOSS. For instance, it's the/bin/sh
(where it replaced the Bourne shell,/usr/xpg4/bin/sh
, the POSIX shell is still based onksh88
) andksh
ofSolaris 11
. Its arrays extend and enhance ksh88's.a=(x y)
can be used to define an array, but sincea=(...)
is also used to define compound variables (a=(foo=bar bar=baz)
),a=()
is ambiguous and declares a compound variable, not an array.- arrays are multi-dimensional (
a=((0 1) (0 2))
) and array elements can also be compound variables (a=((a b) (c=d d=f)); echo "$a[1].c"
). - A
a=([2]=foo [5]=bar)
syntax can be used to define sparse arrays at once. - Size limitations lifted.
- Not to the extent of
zsh
, but great number of operators supported as well to manipulate arrays. "$!a[@]"
to retrieve the list of array indices.- associative arrays also supported as a separate type.
bash
.bash
is the shell of the GNU project. It's used assh
on recent versions of OS/X and some GNU/Linux distributions.bash
arrays mostly emulateksh88
ones with some features ofksh93
andzsh
.a=(x y)
supported.set -A a x y
not supported.a=()
creates an empty array (no compound variables inbash
)."$!a[@]"
for the list of indices.a=([foo]=bar)
syntax supported as well as a few others fromksh93
andzsh
.- recent
bash
versions also support associative arrays as a separate type.
yash
. It's a relatively recent, clean, multi-byte aware POSIX sh implementation. Not in wide use. Its arrays are another clean API similar tozsh
- arrays are not sparse
- defined (and declared) with
a=(var value)
- elements inserted, deleted or modified with the
array
builtin array -s a 5 value
to modify the 5th element would fail if that element was not assigned beforehand.- the number of elements in the array is
$a[#]
,$#a[@]
being the size of the elements as a list. - arrays are a separate type. You need
a=("$a")
to redefine a scalar variable as an array before you can add or modify elements. - arrays are not supported when invoked as
sh
.
So, from that you can see that detecting for array support, which you could do with:
if (unset a; set -A a a; eval "a=(a b)"; eval '[ -n "$a[1]" ]'
) > /dev/null 2>&1
then
array_supported=true
else
array_supported=false
fi
is not enough to be able to use those arrays. You'd need to define wrapper commands to assign arrays as a whole and individual elements, and make sure you don't attempt to create sparse arrays.
Like
unset a
array_elements() eval "REPLY="$#$1[@]"";
if (set -A a -- a) 2> /dev/null; then
set -A a -- a b
case $a[0]$a[1] in
--) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=0;;
a) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[1+($2)]=$3";
first_indice=1;;
--a) set_array() eval "shift; set -A $1"' "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
ab) set_array() eval "shift; set -A $1"' -- "$@"';
set_array_element() eval "$1[$2]=$3";
first_indice=0;;
esac
elif (eval 'a[5]=x') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element() eval "$1[$2]=$3";
first_indice=0
elif (eval 'a=(x) && array -s a 1 y && [ "$a[1]" = y ]') 2> /dev/null; then
set_array() eval "shift; $1=("'"$@")';
set_array_element()
eval "
$1=($$1+"$$1[@]"'")
while [ "$(($2))" -ge "$'"$1"'[#]" ]; do
array -i "$1" "$2" ""
done'
array -s -- "$1" "$((1+$2))" "$3"
array_elements() eval "REPLY=$$1[#]";
first_indice=1
else
echo >&2 "Array not supported"
fi
And then you access array elements with "$a[$first_indice+n]"
, the whole list with "$a[@]"
and use the wrapper functions (array_elements
, set_array
, set_array_element
) to get the number of elements of an array (in $REPLY
), set the array as a whole or assign individual elements.
Probably not worth the effort. I'd use perl
or limit to the Bourne/POSIX shell array: "$@"
.
If the intent is to have some file to be sourced by the interactive shell of a user to define functions that internally use arrays, here are a few more notes that may be useful.
You can configure zsh
arrays to be more like ksh
arrays in local scopes (in functions or anonymous functions).
myfunction()
[ -z "$ZSH_VERSION" ]
You can also emulate ksh
(improve compatibility with ksh
for arrays and several other areas) with:
myfunction() emulate -L ksh
# ksh code more likely to work here
With that in mind and you're willing to drop support for yash
and ksh88
and older versions of pdksh
derivatives, and as long as you don't try to create sparse arrays, you should be able to consistently use:
a[0]=foo
a=(foo bar)
(but nota=()
)$a[#]
,"$a[@]"
,"$a[0]"
in those functions that have the emulate -L ksh
, while the zsh
user still using his/her arrays normally the zsh way.
edited Oct 23 '15 at 20:09
answered Oct 23 '15 at 12:18
Stéphane ChazelasStéphane Chazelas
314k57594952
314k57594952
add a comment |
add a comment |
You can use eval
to try the array syntax:
is_array_support() (
eval 'a=(1)'
) >/dev/null 2>&1
if is_array_support; then
echo support
else
echo not
fi
2
ksh88
supports arrays but nota=()
. Inksh93
,a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.
– Stéphane Chazelas
Oct 23 '15 at 10:13
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Inyash
, you don't doa[5]=1
butarray -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable inksh93
made me surprise, would you mind giving me part of documentation about it. I add1
to the array to make it work.
– cuonglm
Oct 23 '15 at 10:35
|
show 1 more comment
You can use eval
to try the array syntax:
is_array_support() (
eval 'a=(1)'
) >/dev/null 2>&1
if is_array_support; then
echo support
else
echo not
fi
2
ksh88
supports arrays but nota=()
. Inksh93
,a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.
– Stéphane Chazelas
Oct 23 '15 at 10:13
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Inyash
, you don't doa[5]=1
butarray -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable inksh93
made me surprise, would you mind giving me part of documentation about it. I add1
to the array to make it work.
– cuonglm
Oct 23 '15 at 10:35
|
show 1 more comment
You can use eval
to try the array syntax:
is_array_support() (
eval 'a=(1)'
) >/dev/null 2>&1
if is_array_support; then
echo support
else
echo not
fi
You can use eval
to try the array syntax:
is_array_support() (
eval 'a=(1)'
) >/dev/null 2>&1
if is_array_support; then
echo support
else
echo not
fi
edited Oct 23 '15 at 10:33
answered Oct 23 '15 at 8:59
cuonglmcuonglm
106k25211309
106k25211309
2
ksh88
supports arrays but nota=()
. Inksh93
,a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.
– Stéphane Chazelas
Oct 23 '15 at 10:13
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Inyash
, you don't doa[5]=1
butarray -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable inksh93
made me surprise, would you mind giving me part of documentation about it. I add1
to the array to make it work.
– cuonglm
Oct 23 '15 at 10:35
|
show 1 more comment
2
ksh88
supports arrays but nota=()
. Inksh93
,a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.
– Stéphane Chazelas
Oct 23 '15 at 10:13
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Inyash
, you don't doa[5]=1
butarray -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable inksh93
made me surprise, would you mind giving me part of documentation about it. I add1
to the array to make it work.
– cuonglm
Oct 23 '15 at 10:35
2
2
ksh88
supports arrays but not a=()
. In ksh93
, a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.– Stéphane Chazelas
Oct 23 '15 at 10:13
ksh88
supports arrays but not a=()
. In ksh93
, a=()
declares a compound variable, not an array unless the variable has been declared as an array beforehand.– Stéphane Chazelas
Oct 23 '15 at 10:13
2
2
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
Also note that there are significant differences between array implementations. For instance, some have array indices starting at 0 (bash, ksh, zsh in ksh emulation), some starting at one (zsh, yash). Some are normal arrays/lists, some are sparse arrays (associative arrays with keys limited to positive integers like in ksh or bash).
– Stéphane Chazelas
Oct 23 '15 at 10:15
In
yash
, you don't do a[5]=1
but array -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
In
yash
, you don't do a[5]=1
but array -s a 5 1
– Stéphane Chazelas
Oct 23 '15 at 10:21
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: thanks for the precisions. In my case everything boils down to whether arrays (associative or not) are supported at all. Details about index-base can be easily worked out even in a script meant to run unattended.
– Cbhihe
Oct 23 '15 at 10:24
@StéphaneChazelas: The compound variable in
ksh93
made me surprise, would you mind giving me part of documentation about it. I add 1
to the array to make it work.– cuonglm
Oct 23 '15 at 10:35
@StéphaneChazelas: The compound variable in
ksh93
made me surprise, would you mind giving me part of documentation about it. I add 1
to the array to make it work.– cuonglm
Oct 23 '15 at 10:35
|
show 1 more comment
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-array, shell, shell-script
I assume you want to limit to Bourne-like shells?
– Stéphane Chazelas
Oct 23 '15 at 10:17
@StéphaneChazelas: Yes, if you mean (not exhaustively) the core group made of : sh, csh, ksh, tcsh, bash, zsh and close friends. I don't know where yash positions itself in this constellation.
– Cbhihe
Oct 23 '15 at 10:30
2
csh
is not a bourne shell.tcsh
isn't one either (it'scsh
with some bugs fixed)– cas
Oct 23 '15 at 10:42
1
Note that
$SHELL
is the prefered shell of the user, like$EDITOR
is his preferred text editor. It has little to do with the currently running shell.– Stéphane Chazelas
Oct 23 '15 at 13:59
1
eval
uating the output of$SHELL --version
as shell code doesn't make sense.– Stéphane Chazelas
Oct 23 '15 at 14:00