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
134
questions
-1
votes
1answer
26 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 [ $...
0
votes
0answers
22 views
dash: How can I quote the arguments ala “${(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 <...
0
votes
1answer
34 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` ...
...
2
votes
1answer
39 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/...
1
vote
0answers
46 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' ...
0
votes
1answer
85 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 ...
0
votes
1answer
25 views
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.
-2
votes
2answers
62 views
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 ...
3
votes
1answer
1k views
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 ...
1
vote
0answers
19 views
length of the command line buffer [duplicate]
Which's the length of the command line buffer, per shell... and per operating system (if applicable)?
Mostly interested in contemporary versions of Dash and Bash and Debian and macOS, but if anyone ...
2
votes
2answers
222 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 ...
0
votes
1answer
139 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 ...
1
vote
1answer
204 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 [...
2
votes
1answer
61 views
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 ...
6
votes
2answers
957 views
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
/...
5
votes
2answers
257 views
Is there a way to make the local command work portably to dash ksh bash and zsh?
In dash (and in bash zsh and some other shells) the command local works to make a variable scope limited to that function (and descendants in some cases). That enable the possibility of making a ...
4
votes
2answers
235 views
Why the parent shell here-document not work for sub-command in dash but bash work?
I'm run on debian stretch, all below commands(dash and bash) is input to bash.
The whoami seem never run as the user test in dash as in below codes.
$ sudo dash << 'end'
> su test
> ...
3
votes
1answer
240 views
Putting “$@” in a local variable in dash
I have a Bash function that does some string manipulation on its arguments as a whole ("$@") by putting it in a local variable, something like this:
#!/bin/sh
my_func() {
local args="$@"
...
0
votes
3answers
924 views
I would like to check if a file name matches a certain pattern
I would like to check if a file name matches a certain pattern start with an alphanumeric character ([a-zA-Z0-9]) and will only contain alpha-numeric characters plus '.', '-' and '_' characters.
...
8
votes
2answers
300 views
dash not expanding glob wildcards in chroot
I'm working with a copy of Raspbian, installed with pi-gen. Pi-gen runs in a Docker container with a volume for the filesystem, running debootstrap and custom scripts inside a chroot to the volume.
I'...
5
votes
3answers
2k views
Why does ''cat "${1:-/dev/stdin} | … &>/dev/null'' work in bash but not dash?
Script:
#!/bin/sh
#
# reads stdin/file and copies it to clipboard
# clears it after 30s
#
cat "${1:-/dev/stdin}" | timeout 30 xclip -i -selection clipboard -r -verbose &>/dev/null &
I ...
6
votes
3answers
733 views
Shell builtin `printf` line limit?
The /usr/bin/printf util argument list length is limited to the shell's maximum command line length, (i.e. getconf ARG_MAX, on my system that'd be 2097152); example:
# try using a list that's way too ...
1
vote
1answer
336 views
Exit status of chained commands
I want to run a potentially invalid command in a variable cmd. I can't afford to have it just fail me and retrieve the exit status. What I can try to do is pipe it to : and then I'll have a successful ...
0
votes
1answer
64 views
Why can't echo and printf output variables that have only whitespace characters? [duplicate]
var1=$(printf "\n\x0A\n")
var2=$(printf "\na\nb\nc")
Using Android Terminal, the output of echo -e "$var1" (same for echo and printf) iss nothing, not even the 3 new lines. But echo -e "$var2" or ...
3
votes
1answer
2k views
dash: why am I getting the error “Syntax error: EOF in backquote substitution” when my script doesn't even contain a backquote?
#!/bin/sh --
for set_trap_sig in HUP INT QUIT ALRM TERM; do
trap -- '
trap -- - '"${set_trap_sig:?}"' EXIT || exit "$?"
kill -s '"${set_trap_sig:?}"' -- "$$" || exit "$?"' "$...
1
vote
1answer
33 views
How to not split words [duplicate]
I have a list of commands in a file called cmds, one command per line.
I want to grab the last command, set it in a variable last_command and run it later. with $last_command or "$last_command", or ...
2
votes
2answers
567 views
Using diff to compare the output of two commands
How does one go about using diff to compare the output of two commands?
I know how to use it to compare the contents of a file filename1 with the output of a command cmd2:
cmd | diff filename -
How ...
1
vote
2answers
223 views
Escaping spaces in dash [duplicate]
I want to do something like this.
$ touch a\ b
$ cmd=cat\ a\ b
$ echo $cmd
cat a b
$cmd
cat: a: No such file or directory
cat: b: No such file or directory
There are problems with the spaces in the ...
5
votes
1answer
187 views
dash maximum variable length under systemd
I have a shell script that uses a single variable as an associative array (one KEY=VALUE per line).
Throughout the execution of the script, the variable is manipulated to add, remove or modify ...
0
votes
0answers
245 views
History not working in a Dash i-shell (with Bash as a parent process)
My terminal initializes with Bash. I run dash and enter an interactive Dash shell. I run a few random commands and try to run history only for it to fail. I check if history is enabled and it ...
2
votes
2answers
99 views
How do ranges in dash work?
I'm trying to figure out how to rush the following bash script in dash.
for x in {1..5}
do
for y in {a..c}
do
echo $HOME$x$y
done
done
Dash does not support brace expansion and I don'...
4
votes
3answers
724 views
How to escape the null character in here-document?(bash and/or dash)
I want to perform shuf --zero-terminated on multi-line strings with here-document.
5
votes
1answer
930 views
What's going on with this dash '-' thing?
I was trying to export the Python environment requirements and this is what I intended to do:
conda list -e > requirements.txt
However I mistakenly typed this instead:
conda list -e -> ...
2
votes
1answer
326 views
Dash - how to escape strange path characters
If the follow strange directory is created:
a"ā¤
b"
In bash or zsh one can do:
cd a$'\n'b or
cd 'a'$'\n''b'
What is the equivalent for dash?
7
votes
5answers
1k views
Portable check empty directory
With Bash and Dash, you can check for an empty directory using just the shell
(ignore dotfiles to keep things simple):
set *
if [ -e "$1" ]
then
echo 'not empty'
else
echo 'empty'
fi
However I ...
1
vote
1answer
405 views
Can't change shell from dash to bash on Linux Mint VM [closed]
Just installed a virtual machine via virtualbox yesterday and I'm having trouble switching the shell from dash to bash. I've tried chsh as well as modifying the file directly, but it still defaults to ...
0
votes
1answer
91 views
Bash command āresetā ā dash (sh) equivalent?
When the fonts get messed up in dash (jackpal.androidterm), how do I reset that one?
When printing contents of binary files, special characters can mess up the terminal character set. How can this be ...
1
vote
1answer
165 views
some sed commands fail when in background
Some sed commands seem to fail when run in background. Minimal example below.
One sed command appends append after a block of lines that begin with a star *. The other just substitutes a word. The ...
6
votes
2answers
165 views
Is it normal that bash stat() and access() much, before commands?
Running strace on the bash shell that is instructed to run mkdir provided this output which shows lots of stats prior to execve the actual mkdir binary:
BASH$> strace -f sh -c "bash -c \"mkdir /...
1
vote
2answers
276 views
How to check left command's exit status in pipe “left | right” in dash when left command produces large output
It seems that the variable "PIPESTATUS" is unavailable in dash.
Simple separate execution is not working because the left command produces very large output. I used a fifo to do this task:
#!/bin/...
1
vote
1answer
809 views
Is there an invoked file for dash and sh as non login shells in /etc directory?
/etc/profile can be invoked by sh and dash inside an interactive login mode. Is there any file in /etc directory to be invoked when they are in an interactive non-login mode?
1
vote
1answer
371 views
Using the 'a' and 'c' options with the 'dash' command in Unix [closed]
What do the options 'a' and 'c' do when there are used with the command 'dash'? I was unable to understand what that command actually does! I have tried reading the man page but didn't exactly ...
1
vote
4answers
2k views
dash: read variable from pipe
In bash or zsh, I can use following syntax to read from pipe into variables:
echo AAA BBB | read X Y ; echo $X
which will print AAA
Why does the same not work in /bin/sh?
I am using /bin/sh -> /...
1
vote
1answer
347 views
How can I set PATH in the `dash`(or bash) shell so that it doesn't search any dirs ? because empty PATH searches current directory
In Dash if I set the PATH to an empty string, it searches in current directory:
$ export PATH=
$ echo $PATH
$ emptyexe
$ /usr/bin/ls emptyexe
emptyexe
$ pwd
/home/ctor
$ cd ..
$ emptyexe
dash: 36: ...
0
votes
1answer
43 views
Where is '/?' parameter expansion documented?
I came across this weird parameter expansion for bash/dash which I don't find any reference for. What is this sort of expansion called? Where is it documented?
$ /???
bash: /bin: Is a directory
$ /???...
1
vote
0answers
408 views
Dash escaping hyphen?
I am using Homebrews dash package on MacOS to print a text.
echo "Hello World - Test"
But I am receiving
Hello World \- Test
What am I doing wrong?
0
votes
1answer
79 views
POSIX-ly correct way to isolate files with newlines via find?
There's a question How to find files that contain newline in filename?, where the accepted answer handles isolating files with newlines via ANSI-C quoting, and that works fine in ksh and bash, but how ...
8
votes
1answer
740 views
Is parameter expansion on $@ not supported by the sh shell?
I posted an answer to a question on AU, and I found that parameter expansion on $@ doesn't work with the sh shell:
<infile xargs -d'\n' sh -c 'echo "${@%%/*}"' _
but it works fine in bash. Is ...
1
vote
1answer
2k views
BASH/DASH: What is the best way to pass array to function?
I have this array:
PARAMETERS_OF_COMPONENTS[1]="component1"
PARAMETERS_OF_COMPONENTS[2]="component21 component22 component23"
PARAMETERS_OF_COMPONENTS[3]="component3"
PARAMETERS_OF_COMPONENTS[4]="...
2
votes
1answer
540 views
Dash “-nt” behavior
The use case I can think of for -nt, would be updating a file if it is too
old, or if it does not exist. Bash handles this just fine:
$ bash -c 'touch 2.txt; sleep 1; touch 1.txt; [ 1.txt -nt 2.txt ];...
