The function below was originally a bash function. I need it to run in busybox 1.22 ash shell.
dockerip() {
if (( $# != 1 ))
then
for d in $(docker ps -q)
do
name=$(docker inspect -f {{.Name}} $d)
ip=$(docker inspect -f {{.NetworkSettings.IPAddress}} $d)
printf "%-15s | %15s\n" $name $ip
done
fi
}
When the code above is loaded with source and run as dockerip the busybox shell outputs: sh: 0: not found. Not a very helpful error so my question is what does the error mean and what part(s) of the function above aren't busybox 1.22 compatible?
This arithmetic expression (( $# != 1 )) is bash syntax. In ash, it's launching 2 nested subshells, then executing the program "$#" with arguments "!=" and "1".
Use this instead
if [ $# -ne 1 ]
Related
I got some code from here that works pretty well until I get "Argument list too long"
I am NOT a developer and pretty old too :) so if it is not much to ask please explain.
Is there a way the expand DIRCMD like eval does and pass each of the commands one at the time so eval does not break?
for (( ifl=0;ifl<$((NUMFIRSTLEVELDIRS));ifl++ )) { FLDIR="$(get_rand_dirname)"
FLCHILDREN="";
for (( ird=0;ird<$((DIRDEPTH-1));ird++ )) {
DIRCHILDREN=""; MOREDC=0;
for ((idc=0; idc<$((MINDIRCHILDREN+RANDOM%MAXDIRCHILDREN)); idc++)) {
CDIR="$(get_rand_dirname)" ;
# make sure comma is last, so brace expansion works even for 1 element? that can mess with expansion math, though
if [ "$DIRCHILDREN" == "" ]; then
DIRCHILDREN="\"$CDIR\"" ;
else
DIRCHILDREN="$DIRCHILDREN,\"$CDIR\"" ;
MOREDC=1 ;
fi
}
if [ "$MOREDC" == "1" ] ; then
if [ "$FLCHILDREN" == "" ]; then
FLCHILDREN="{$DIRCHILDREN}" ;
else
FLCHILDREN="$FLCHILDREN/{$DIRCHILDREN}" ;
fi
else
if [ "$FLCHILDREN" == "" ]; then
FLCHILDREN="$DIRCHILDREN" ;
else
FLCHILDREN="$FLCHILDREN/$DIRCHILDREN" ;
fi
fi
}
cd $OUTDIR
DIRCMD="mkdir -p $OUTDIR/\"$FLDIR\"/$FLCHILDREN"
eval "$DIRCMD"
echo "$DIRCMD"
}
I tried echo $DIRCMD but do not get the expanded list of commands
'echo mkdir -p /mnt/nvme-test/rndpath/"r8oF"/{"rc","XXKR","p0H"}/{"5Dw0K","oT","rV","coU","uo"}/{"3m5m","uEdA","w4SJp","49"}'
I had trouble following the code, but if I understood it correctly, you dynamically generate a mkdir -p command with a brace expansion:
'mkdir -p /mnt/nvme-test/rndpath/"r8oF"/{"rc","XXKR","p0H"}/{"5Dw0K","oT","rV","coU","uo"}/{"3m5m","uEdA","w4SJp","49"}'
Which then fails when you eval it due to your OS' maximum argument limit.
To get around that, you can instead generate a printf .. command since this is a Bash builtin and not subject to the argument limit, and feed its output to xargs:
dircmd='printf "%s\0" /mnt/nvme-test/rndpath/"r8oF"/{"rc","XXKR","p0H"}/{"5Dw0K","oT","rV","coU","uo"}/{"3m5m","uEdA","w4SJp","49"}'
eval "$dircmd" | xargs -0 mkdir -p
If your xargs doesn't support -0, you can instead use printf "%s\n" and xargs mkdir -p, though it won't behave as well if your generated names contain spaces and such.
If this is for benchmarking, you may additionally be interested to know that you can now use xargs -0 -n 1000 -P 8 mkdir -p to run 8 mkdirs in parallel, each creating 1000 dirs at a time.
[Arch Linux v5.0.7 with GNU bash 5.0.3]
Some .bashrc aliases seem to conflict with a bash shell-scripts provided by pyenv and pyenv-virtualenvwrapper.I tracked down the problem running the script, using set -x and with all aliases enabled, and saw finally that the script exits gracefully with exit code is 0 only when aliases are disabled with unalias -a. So this has to do with aliases... but which one ?
To try to automate that, I wrote the shell-script below:
It un-aliases one alias at a time, reading iteratively from the complete list of aliases,
It tests the conflicting shell script test.sh against that leave-one-out alias configuration, and prints something in case an error is detected,
It undoes the previous un-aliasing,
It goes on to un-aliasing the next alias.
But the two built-ins alias and unalias do not fare well in the script cac.sh below:
#! /usr/bin/bash
[ -e aliases.txt ] && rm -f aliases.txt
alias | sed 's/alias //' | cut -d "=" -f1 > aliases.txt
printf "File aliases.txt created with %d lines.\n" \
"$(wc -l < <(\cat aliases.txt))"
IFS=" "
n=0
while read -r line || [ -n "$line" ]; do
n=$((n+1))
aliasedAs=$( alias "$line" | sed 's/alias //' )
printf "Line %2d: %s\n" "$n" "$aliasedAs"
unalias "$line"
[ -z $(eval "$*" 1> /dev/null) ] \ # check output to stderr only
&& printf "********** Look up: %s\n" "$line"
eval "${aliasedAs}"
done < <(tail aliases.txt) # use tail + proc substitution for testing only
Use the script like so: $ cac.sh test.sh [optional arguments to test.sh] Any test.sh will do. It just needs to return some non-empty string to stderr.
The first anomaly is that the file aliases.txt is empty as if the alias builtin was not accessible from within the script. If I start the script from its 3rd line, using an already populated aliases.txt file, the script fails at the second line within the while block, again as if alias could not be called from within the script. Any suggestions appreciated.
Note: The one liner below works in console:
$ n=0;while read -r line || [ -n "$line" ]; do n=$((n+1)); printf "alias %d : %s\n" "$n" "$(alias "$line" | sed 's/alias //')"; done < aliases.txt
I would generally advise against implementing this as an external script at all -- it makes much more sense as a function that can be evaluated directly in your interactive shell (which is, after all, where all the potentially-involved aliases are defined).
print_result() {
local prior_retval=$? label=$1
if (( prior_retval == 0 )); then
printf '%-30s - %s\n' "$label" WORKS >&2
else
printf '%-30s - %s\n' "$label" BROKEN >&2
fi
}
test_without_each_alias() {
[ "$#" = 1 ] || { echo "Usage: test_without_each_alias 'code here'" >&2; return 1; }
local alias
(eval "$1"); print_result "Unchanged aliases"
for alias in "${!BASH_ALIASES[#]}"; do
(unalias "$alias" && eval "$1"); print_result "Without $alias"
done
}
Consider the following:
rm_in_home_only() { [[ $1 = /home/* ]] || return 1; rm -- "$#"; }
alias rm=rm_in_home_only # alias actually causing our bug
alias red_herring=true # another alias that's harmless
test_without_each_alias 'touch /tmp/foobar; rm /tmp/foobar; [[ ! -e /tmp/foobar ]]'
...which emits something like:
Unchanged aliases - BROKEN
Without rm - WORKS
Without red_herring - BROKEN
Note that if the code you pass executes a function, you'll want to be sure that the function is defined inside the eval'd code; since aliases are parser behavior, they take place when functions are defined, not when functions are run.
#Kamil_Cuk, #Benjamin_W and #cdarke all pointed to the fact that a noninteractive shell (as that spawned from a bash script) does not have access to aliases.
#CharlesDuffy pointed to probable word splitting and glob expansion resulting in something that could be invalid test syntax in the original [ -z $(eval "$*" 1> /dev/null) ] block above, or worse yet in the possibility of $(eval "$*" 1> /dev/null) being parsed as a glob resulting in unpredictable script behavior. Block corrected to: [ -z "$(eval "$*" 1> /dev/null)" ].
Making the shell spawned by cac.sh interactive, with #! /usr/bin/bash -i. make the two built-ins alias and unalias returned non-null result when invoked, and BASH_ALIASES[#] became accessible from within the script.
#! /usr/bin/bash -i
[ -e aliases.txt ] && rm -f aliases.txt
alias | sed 's/alias //' | cut -d "=" -f1 > aliases.txt
printf "File aliases.txt created with %d lines.\n" \
"$(wc -l < <(\cat aliases.txt))"
IFS=" "
while read -r line || [ -n "$line" ]; do
aliasedAs=$( alias "$line" | sed 's/alias //' )
unalias "$line"
[ -z "$(eval "$*" 2>&1 1>/dev/null)" ] \ # check output to stderr only
&& printf "********** Look up: %s\n" "$line"
eval "${aliasedAs}"
done < aliases.txt
Warning: testing test.sh resorts to the eval built-in. Arbitrary code can be executed on your system if test.sh and optional arguments do not come from a trusted source.
In specifically Bash version 4.0.0, is there any way to work around the use of an empty $# raising an unbound variable error when set -u is enabled?
Consider the following:
#!/usr/bin/env bash-4.0.0-1
set -xvu
echo "$BASH_VERSION"
echo "${BASH_VERSINFO[#]}"
main () {
printf '%q\n' "${#:-}"
}
main "${#:-}"
Gives me the following output when I provide an empty set of arguments:
neech#nicolaw.uk:~ $ ./test.sh
echo "$BASH_VERSION"
+ echo '4.0.0(1)-release'
4.0.0(1)-release
echo "${BASH_VERSINFO[#]}"
+ echo 4 0 0 1 release x86_64-unknown-linux-gnu
4 0 0 1 release x86_64-unknown-linux-gnu
main () {
printf '%q\n' "${#:-}"
}
main "${#:-}"
./test.sh: line 12: $#: unbound variable
I only see this behaviour in Bash version 4.0.0.
I was hoping that using variable substitution ${#:-} would allow me to work around this, but it seems not.
Is there a way to work around this?
$#, $* are special variables so should always be defined it's a bug
https://unix.stackexchange.com/questions/16560/bash-su-unbound-variable-with-set-u
a workaround, maybe:
set +u
args=("$#")
set -u
main "${args[#]}"
or maybe also
main "${#:+$#}"
Why not do error handling on your own? This way you can control exactly what happens when an exception is encountered, for instance return a custom exit code and message for that error, rather than be confined to some predefined behavior.
function log_error
{
[[ $# -ne 1 ]] && return 1
typeset msg="$1"
typeset timestamp=$(date "+%F %T")
echo "[${timestamp}] [ERROR] - $msg " >&2
}
if [[ -z "$BASH_VERSION" ]]
then
log_error "BASH VERSION is not set"
exit 1
fi
The set command can be used to change values of the positional arguments $1 $2 ...
But, is there any way to change $0 ?
In Bash greater than or equal to 5 you can change $0 like this:
$ cat bar.sh
#!/bin/bash
echo $0
BASH_ARGV0=lol
echo $0
$ ./bar.sh
./bar.sh
lol
ZSH even supports assigning directly to 0:
$ cat foo.zsh
#!/bin/zsh
echo $0
0=lol
echo $0
$ ./foo.zsh
./foo.zsh
lol
Here is another method. It is implemented through direct commands execution which is somewhat better than sourcing (the dot command). But, this method works only for shell interpreter, not bash, since sh supports -s -c options passed together:
#! /bin/sh
# try executing this script with several arguments to see the effect
test ".$INNERCALL" = .YES || {
export INNERCALL=YES
cat "$0" | /bin/sh -s -c : argv0new "$#"
exit $?
}
printf "argv[0]=$0\n"
i=1 ; for arg in "$#" ; do printf "argv[$i]=$arg\n" ; i=`expr $i + 1` ; done
The expected output of the both examples in case ./the_example.sh 1 2 3 should be:
argv[0]=argv0new
argv[1]=1
argv[2]=2
argv[3]=3
#! /bin/sh
# try executing this script with several arguments to see the effect
test ".$INNERCALL" = .YES || {
export INNERCALL=YES
# this method works both for shell and bash interpreters
sh -c ". '$0'" argv0new "$#"
exit $?
}
printf "argv[0]=$0\n"
i=1 ; for arg in "$#" ; do printf "argv[$i]=$arg\n" ; i=`expr $i + 1` ; done
How can I check in bash and csh if commands are builtin? Is there a method compatible with most shells?
You can try using which in csh or type in bash. If something is a built-in command, it will say so; otherwise, you get the location of the command in your PATH.
In csh:
# which echo
echo: shell built-in command.
# which parted
/sbin/parted
In bash:
# type echo
echo is a shell builtin
# type parted
parted is /sbin/parted
type might also show something like this:
# type clear
clear is hashed (/usr/bin/clear)
...which means that it's not a built-in, but that bash has stored its location in a hashtable to speed up access to it; (a little bit) more in this post on Unix & Linux.
In bash, you can use the type command with the -t option. Full details can be found in the bash-builtins man page but the relevant bit is:
type -t name
If the -t option is used, type prints a string which is one of alias, keyword, function, builtin, or file if name is an alias, shell reserved word, function, builtin, or disk file, respectively. If the name is not found, then nothing is printed, and an exit status of false is returned.
Hence you can use a check such as:
if [[ "$(type -t read)" == "builtin" ]] ; then echo read ; fi
if [[ "$(type -t cd)" == "builtin" ]] ; then echo cd ; fi
if [[ "$(type -t ls)" == "builtin" ]] ; then echo ls ; fi
which would result in the output:
read
cd
For bash, use type command
For csh, you can use:
which command-name
If it's built-in, it will tell so.
Not sure if it works the same for bash.
We careful with aliases, though. There may be options for that.
The other answers here are close, but they all fail if there is an alias or function with the same name as the command you're checking.
Here's my solution:
In tcsh
Use the where command, which gives all occurrences of the command name, including whether it's a built-in. Then grep to see if one of the lines says that it's a built-in.
alias isbuiltin 'test \!:1 != "builtin" && where \!:1 | egrep "built-?in" > /dev/null || echo \!:1" is not a built-in"'
In bash/zsh
Use type -a, which gives all occurrences of the command name, including whether it's a built-in. Then grep to see if one of the lines says that it's a built-in.
isbuiltin() {
if [[ $# -ne 1 ]]; then
echo "Usage: $0 command"
return 1
fi
cmd=$1
if ! type -a $cmd 2> /dev/null | egrep '\<built-?in\>' > /dev/null
then
printf "$cmd is not a built-in\n" >&2
return 1
fi
return 0
}
In ksh88/ksh93
Open a sub-shell so that you can remove any aliases or command names of the same name. Then in the subshell, use whence -v. There's also some extra archaic syntax in this solution to support ksh88.
isbuiltin() {
if [[ $# -ne 1 ]]; then
echo "Usage: $0 command"
return 1
fi
cmd=$1
if (
#Open a subshell so that aliases and functions can be safely removed,
# allowing `whence -v` to see the built-in command if there is one.
unalias "$cmd";
if [[ "$cmd" != '.' ]] && typeset -f | egrep "^(function *$cmd|$cmd\(\))" > /dev/null 2>&1
then
#Remove the function iff it exists.
#Since `unset` is a special built-in, the subshell dies if it fails
unset -f "$cmd";
fi
PATH='/no';
#NOTE: we can't use `whence -a` because it's not supported in older versions of ksh
whence -v "$cmd" 2>&1
) 2> /dev/null | grep -v 'not found' | grep 'builtin' > /dev/null 2>&1
then
#No-op
:
else
printf "$cmd is not a built-in\n" >&2
return 1
fi
}
Using the Solution
Once you applied the aforementioned solution in the shell of your choice, you can use it like this...
At the command line:
$ isbuiltin command
If the command is a built-in, it prints nothing; otherwise, it prints a message to stderr.
Or you can use it like this in a script:
if isbuiltin $cmd 2> /dev/null
then
echo "$cmd is a built-in"
else
echo "$cmd is NOT a built-in"
fi