Questions tagged [dash]
The Dash shell, a POSIX-compliant derivative of the Almquist shell used as /bin/sh in Debian, Ubuntu and other Linux distributions
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dash script replace array
This script works if I use bash on my Debian 11 (bullseye). But now I need to refactor it to use Debian's sh shell(/bin/dash).
#!/bin/dash
var1=1
var2=2
var3=3
arr=($var1 $var2 $var3)
exist_var=&...
- 95
7
votes
2
answers
1k
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How do I keep a dash shell script running despite any error?
I have a dash shell script that is intended to run to the end of file:
#!/usr/bin/dash
# File b_shell
. a_nonexistent_file
echo "I want to print this line despite any previous error."
...
- 171
2
votes
1
answer
63
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How to add a substring to a string as a column
The title may not be the best at describing the issue, but this was the best I could come up with, moving on to describe what I'm trying to do, I use artix runit as my os, and it is tedious to create ...
- 23
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0
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47
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Anyway to bind keyboard to dash (Debian Almquist Shell)?
Specifically Up/Down for history navigation.
What I already know
I understand dash is a minimalistic, no bloat, (somewhat) strict POSIX shell.
I understand the philosophy behind it, and the reason ...
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3
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1
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396
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Why is "${1-"$var"}" (option 6 down below) not mentioned in POSIX?
The only reference I could find in the spec is this:
It would be desirable to include the statement "The characters from an enclosed "${" to the matching '}' shall not be affected by ...
- 1,973
3
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1
answer
479
views
Debian /bin/sh in a Docker container never seems to look at .profile
I can not seem to get dash to look at $HOME/.profile:
pedz@Peace:s001 ~[S:hatred] % docker exec -it hatred-web-1 dash -i
# cat $HOME/.profile
PROOF=true; export PROOF
PATH=/hatred/bin:$PATH; export ...
- 173
1
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1
answer
994
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Multiple commands in variable? [duplicate]
Is it possible to execute multiple commands stored in a variable?
Singe command works fine
variable="echo HELLO"
$variable
HELLO
I would like to have something like this
variable="...
user542537
7
votes
2
answers
590
views
Is there a pipefail equivalent for dash?
I have a perl script that runs a system() call to execute shell commands and I would like to run more than one command and pipe data between them. Something like (in perl):
system("command1 | ...
- 235k
7
votes
1
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1k
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Why doesn't sudo always spawn a shell sub-process?
I am trying to understand why some shells seem to receive a special treatment when called with sudo. For instance, there seem to be two possible behaviours:
The "implicit" group (pstree is a ...
- 167
1
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1
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316
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Bash for every x files create sub folder and move files there
I am looking for an alternative dash command I can use
as I am trying to execute the code from within python
and due to the fact that the sub folder has 100's of files I am am trying to group into ...
- 31
2
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0
answers
233
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how to close file descriptor bigger then 9 by dash in shell script
I want launch a shell script in code called system("sh example.sh"), and close all file descriptors like this:
for fd in $(ls /proc/$$/fd); do
case "$fd" in
0|1|2)
;;...
- 21
0
votes
2
answers
889
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Sourcing file in dash with . file gives "not found" error
I'm trying to source (bash-parlance) a file in dash using . file as specified by the man page:
. file
The commands in the specified file are read and executed by the
shell.
But I ...
- 265
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1
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453
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What parts of dash are not part of the POSIX standard?
I know that dash adheres quite closely to the POSIX standard, but I know that it's not 100.00% strict POSIX without any extras. The shell that comes closest/adheres exactly to the POSIX standard is as ...
1
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1
answer
314
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SHELLOPTS equivalent for /bin/dash
I have to run a number of shell scripts that are defined by a third party. So I cannot (or would prefer not to) change their content or which shell (bash vs. dash) they are using. They may or may not ...
- 175
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1
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105
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Incorrect order of commands in "Command Substitution" (Bash/Dash)
Why is it that when you run the substitution commands, the order of execution is broken, as in the example below. First the chmod command was executed, then echo 1 and echo 2?
echo $(echo 1; echo 2; ...
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0
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52
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Secure transfer of arguments to a program (dash/bash)
Transfer via stdin
#!/bin/dash
echo 'password' | program -
Transfer via stdin using an intermediate variable
var_pass=$(echo 'password')
echo $var_pass | program -
unset var_pass
Transfer via ...
- 147
1
vote
1
answer
222
views
Proper way to wrap dash using rlwrap
On Ubuntu, I have set alias sh='rlwrap --complete-filenames sh' to get readline keybindings and filename completion when using the dash shell (on my computer, sh is /usr/bin/sh, which is a symbolic ...
- 2,566
-1
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3
answers
88
views
Changing the place operator in a csv file
I've been editing a CSV file so I can import it into postgres. At this point I want to change the operator from column 5 to the left side of the column when the value is negative"-". When it ...
0
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3
answers
78
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find/detect file name goups
On fs i have files like:
PREFIX_GROUPNAME_OTHERNAMES[.txt|.*]
eg:
A_ABC_A.txt
A_ABC_B.txt
A_ABC_C.txt
A_XYZ_A.txt
A_XYZ_B.txt
A_XYZ_C.txt
For some futher tasks i want to get the group names.
$# ...
- 13
2
votes
0
answers
120
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Can't grep or word count the output of jobs command in dash
This is what I tested in Arch's dash shell and FreeBSD's default sh shell, the results are the same.
$ sleep 100 &
$ jobs
[1] + Running sleep 100
$ jobs | wc
0 0 ...
- 121
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1
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purpose of dashes in `wget -qO- https://get.speedify.com | bash -`
In this command:
wget -qO- https://get.speedify.com | bash -
Source: https://support.speedify.com/article/562-install-speedify-linux
...the first -q is the option for "quiet" mode. What is ...
- 2,212
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2k
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ssh: force different shell for non-interactive command execution
how can I force specific shell to be used for non-interactive command execution via ssh on remote server?
My default shell on the remote server is zsh, but I need to execute given command using /bin/...
5
votes
1
answer
1k
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/bin/sh: wildcard expansion does not work in script
I am using dash as /bin/sh. In my script, I have following line:
SSH_AUTH_SOCK=/tmp/ssh-????????????/agent.*
Which is supposed to match file /tmp/ssh-abcdefghijkl/agent.1234. Even when the file ...
0
votes
2
answers
415
views
How to execute a one-line posix dash command within dash script to enable coredump?
For unrelated purposes I am forced to produce a script that only works with posix sh.
Within my script I have checked if the system allows the creation of coredumps, then if the limit is set to 0 I ...
- 19
3
votes
1
answer
93
views
dash and local keyword not resetting shell
dash shell (unlike bash and busybox ash implementation where both examples print foo: '') takes value of previously
defined variable, i.e. guarding with local does not work:
$ foo=ee; bar() { local ...
- 1,397
-1
votes
1
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310
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Having an interactive shell experience but running everything through dash
So i'm starting to get addicted to POSIX standards and simplicity yet i hate not having autocomplete using the arrows to go through characters and i want a cool shell prompt.
so is there anyway that i ...
- 133
0
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0
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161
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Why integer division is faster than bitwise shift in shell?
I'm comparing performance of bash and dash (default sh in Xubuntu 18.04).
I expect sh to be faster than bash
I expect bitwise shift to be faster than division operator.
However, I'm getting ...
1
vote
2
answers
152
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Can't delete multiple files with spaces on name with rm
I'm working on a deploy script for my dotfiles, they are stored on a Git bare repository, from which i git checkout it's files into my home directory, in order to seamlessy do it without thousands of ...
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-4
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1
answer
2k
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How to printf ascii characters with hex or dec inside /bin/sh -c '...'?
/bin/sh would be dash
what is the correct syntax for printf to display certain ascii character using hex or dex code in dash?
let's say i want to printf a dollar sign ($). which hex or dec code should ...
user476578
0
votes
1
answer
345
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Global Variables across scripts [duplicate]
Why is lets say HOME recognized by all my scripts but my variable DMENU isn't?
I export it in my bspwmrc file which is executed at start up.Also had it in my zshrc.
Why do this?
DMENU="-h 27 -z ...
- 143
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1
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153
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su not working inside arch-chroot with dash shell
When i try to do the following inside a dash script:
#!/bin/dash
arch-chroot /mnt /bin/dash <<- EOF
su myuser
whoami
EOF
It simply logs the "root", but when i try to do it ...
- 828
12
votes
2
answers
4k
views
Shell script returns 0 exit_status despite syntax error
Consider this script:
#!/bin/sh
foo=1
if [[ ! -z $foo ]]; then
echo abc
fi
It's using the Bash syntax [[ ... ]] which doesn't work (as expected) when I run it with the default shell on Ubuntu (...
- 233
5
votes
2
answers
922
views
bash -e and && evaluation inside functions
I'm puzzled by bash (and dash) behavior when -e option is set.
Simple example:
#!/bin/bash -e
func() {
false && true
}
false && true
echo "1"
func
echo "2"
...
- 53
2
votes
2
answers
1k
views
/bin/sh evaluates string while Bash does not
When running the script below, I get two different outputs, depending on whether or not the shell used is sh or bash:
regex(){
echo 's/\(.* \)\(!\{0,1\}\)has(/\1\2MOCK_has(/g'
}
replace_builtins(...
- 1,090
1
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1
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148
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Can't use variables while feeding commands to bash through stdin
I need to run a small shell script using C popen call (which calls sh -c '<command>'). I can't get my script to work. I isolated the issue to this snippet:
#!/bin/bash
sh -c 'bash -xev -s <&...
- 121
3
votes
2
answers
595
views
Why does printf byte formatting fail when executed under `dash`?
The ASCII hex code for a zero is 0x30. Hence, you can print a zero by doing printf '\x30', and it will print a zero.
If you put this into a shell script called myScript.sh, and then execute ./myScript....
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-1
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1
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541
views
variable regex test in dash?
I got plenty possible variables in a form of [a-z][0-9], eg 1 letter and 1 number.
Is there a way to test them in dash? Something like:
myvar=o7
if [ $myvar=o[0-4] ]; then
"do this"
elif [ $...
user434951
0
votes
1
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198
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dash: How can I quote the arguments ala "${(q+@)@}" in zsh?
I want to quote the arguments in dash (or sh, or even bash if that's not possible). I can do that with "${(q+@)@}" in zsh, such that reval <sth> ... is the same as just typing in <...
- 1,493
0
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1
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301
views
cmd nested in backticks processed from sudo?
Are nested `commands` using (deprecated) backticks executed with root permissions (from sudo command line) while command substitution $(...) is not?
for example
sudo mount `blkid -u /dev/sda1` ...
...
- 554
2
votes
1
answer
165
views
emulate zsh multios in dash (multiple redirections)
in zsh, when the option multios is enabled, I can pipe output to two different processes, ie:
cat /dev/sda > sda.img | sha256sum > sda.img.sha256
How could I achieve the same in dash, ie /bin/...
2
votes
0
answers
353
views
Trap on DEBUG signal for the ash and dash shells?
With the bash shell, you can install a trap on the synthetic DEBUG signal. This is useful and will execute your function or bit of code on every shell command.
Not so in ash or dash.
$ trap 'echo hi' ...
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1
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955
views
Do all POSIX shells implement arithmetic expansion $((...)) in the same way? [duplicate]
I'm trying to write a shell script which should work under any POSIX shell, and I found what seems to be an odd quirk of dash. I'm wondering whether this is something I can rely on working under other ...
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1
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89
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dash: echo args exactly with no processing
I want to do sth like zsh's print -r -- ... which just echoes the arguments without changing them at all.
printf -- still interprets directives.
- 1,493
0
votes
2
answers
219
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execlp() system call
I want to call the ulimit shell command through a C program. right now, I have:
execlp("ulimit", "ulimit", "-u", "%d", ulimit_a);
It compiles fine, but does not actually edit the user-id max ...
- 31
9
votes
1
answer
7k
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Error sh: 1: read: arg count
I want to simply wait for the user to acknowledge a message by pressing Return. In bash, I am able to call
$ read
$
However, in sh (dash in my case), I get
$ read
sh: 1: read: arg count
$
It ...
- 2,980
2
votes
2
answers
2k
views
Why does SIGTERM work to terminate bash but not ash or dash?
Comparing bash, ash and dash, only bash can be terminated by SIGTERM
kill -TERM <pid>
For ash and bash, I need SIGHUP or SIGKILL
kill -HUP <pid>
kill -KILL <pid>
What's the ...
- 2,980
1
vote
1
answer
846
views
Dash non-interactive non-login rc file
Does dash have a non-interactive non-login rc file? I've read the man page, which recommends .profile for login shells and $ENV environment variable for interactive shells.
Is there anything that ...
- 553
1
vote
1
answer
739
views
How to kill all background jobs in dash?
Simply kill $( jobs -p ) not work in dash.
For example in dash:
$ sleep 999 &
$ kill $(jobs -p)
dash: 2: kill: Usage: kill [-s sigspec | -signum | -sigspec] [pid | job]... or
kill -l [...
- 953
2
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1
answer
211
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No /var/lib/dpkg/info/dash.preinst in Buster
In https://wiki.debian.org/Multistrap#Steps_for_Squeeze_and_later, it's required to run the following command in chroot environment:
/var/lib/dpkg/info/dash.preinst install
This command runs in ...
- 2,251
6
votes
2
answers
1k
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Are shells allowed to ignore NUL bytes in scripts?
Because that's what some of them are doing.
> echo echo Hallo, Baby! | iconv -f utf-8 -t utf-16le > /tmp/hallo
> chmod 755 /tmp/hallo
> dash /tmp/hallo
Hallo, Baby!
> bash /tmp/hallo
/...
user313992