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
7
votes
3answers
323 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 "$1" ]
then
echo 'not empty'
else
echo 'empty'
fi
However I ...
1
vote
1answer
42 views
Can't change shell from dash to bash on Linux Mint VM [closed]
Just installed a virtual machine via virtualbox yesterday and I'm having trouble switching the shell from dash to bash. I've tried chsh as well as modifying the file directly, but it still defaults to ...
-1
votes
1answer
44 views
Bash command “reset” — dash (sh) equivalent?
When the fonts get messed up in dash (jackpal.androidterm), how do I reset that one?
When printing contents of binary files, special characters can mess up the terminal character set. How can this be ...
0
votes
1answer
54 views
some sed commands fail when in background
Some sed commands seem to fail when run in background. Minimal example below.
One sed command appends append after a block of lines that begin with a star *. The other just substitutes a word. The ...
6
votes
2answers
58 views
Is it normal that bash stat() and access() much, before commands?
Running strace on the bash shell that is instructed to run mkdir provided this output which shows lots of stats prior to execve the actual mkdir binary:
BASH$> strace -f sh -c "bash -c \"mkdir /...
1
vote
2answers
89 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/...
0
votes
1answer
62 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
63 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
90 views
/bin/sh: read variable from pipe [duplicate]
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
49 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
36 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
56 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
41 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 ...
7
votes
1answer
443 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
393 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
111 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 ];...
1
vote
1answer
212 views
How do I reliably convert /proc/pid/environ to arguments for the env command?
How do I reliable convert /proc/pid/environ to argument for the env command?
IFS=$'\n' ; env -i $(xargs -0n1 -a /proc/$$/environ) only works when all environment variables do not have the newline ...
7
votes
2answers
759 views
Test if variable contains newline (POSIX)
I know that some shells accept this kind of test:
t() { [[ $var == *$'\n'* ]] && res=yes || res=no
printf '%s ' "$res";
}
var='ab
cd'
t
var='abcd'
t
echo
on execution:
$ bash ./...
3
votes
1answer
111 views
Does fd number of various shells fixed?
Let's say:
xb@dnxb:/tmp$ echo 'ls -l /proc/$$/fd | grep a.sh' > a.sh; \
> while IFS='' read -r f; do \
> echo "$f"; "$f" a.sh; \
> done < <(tail -n +2 /etc/shells)
/bin/sh
lr-x------...
4
votes
1answer
344 views
Why does CDPATH not work as documented in the manuals?
The Bourne Again shell manual says, of cd dir: […] each directory name in CDPATH is searched for dir. […] If dir begins with a slash (/), then CDPATH is not used.
The Z shell manual ...
9
votes
4answers
2k views
Split string on colon in /bin/sh
My dash script takes a parameter in the form of hostname:port, i.e.:
myhost:1234
Whereas port is optional, i.e.:
myhost
I need to read the host and port into separate variables. In the first case, ...
1
vote
1answer
74 views
How to find out the version number of `dash` without resorting to package management systems?
I have been using bash most of the time and has just started playing with other shells. I started with dash and tries to find out its version number but the usual method like -v or $version does not ...
8
votes
1answer
390 views
Why does exiting with a stored returncode of a nested command result in different returncodes in Dash and Bash?
Running
bash -c 'bash -c "echo test1; exit 1;" &> /tmp/x; buildresult=$?; tail -n 100 /tmp/x; exit $buildresult;'
results in test1 being printed to console and echo $? to print 1 which in my ...
4
votes
1answer
2k views
bash command substitution with redirection: bad file descriptor
the following command works in dash but fails in bash with "Bad file descriptor".
$ dash -c 'out=$(echo "to fd3" >&3; echo "to stdout") 3>&1; echo "out: $out"'
to fd3
out: to stdout
$ ...
0
votes
1answer
303 views
Why is using git with && failing when inside a .sh but not from the command line?
I have a script (called update_content.sh) that is supposed to run 3 consecutive git commands and the first version looked like this:
#!/bin/sh
git fetch --all && git reset --hard && ...
1
vote
3answers
475 views
Error cleanup for shell scripts
What's the best way to include error cleanup logic for shell scripts?
Specifically, I have a script that does something like this:
mount a x
mount b y
setup_thing
mount c z
do_something
umount z
...
8
votes
2answers
954 views
How does bash file redirection to standard in differ from shell (`sh`) on Linux?
I wrote a script which switches users while running, and executed it using file redirection to standard in. So user-switch.sh is...
#!/bin/bash
whoami
sudo su -l root
whoami
And running it with ...
0
votes
3answers
121 views
Why does read -r eat text? [duplicate]
I have a names.txt file with with the top line of text being
51 Pipe-line\Closed3\00001011_-_Portfolio\UW\Old\NID50_Future_022814.xlsx
I would like to write new filenames replacing \ with /
I wrote ...
0
votes
1answer
171 views
Going through 2D array
I have an expression
ls -l `find . -type f` | tr -s [:space:] | cut -d ' ' -f 5 | sort | uniq -c | tr -s [:space:] | sort -k 2n
which creates a 2D array like:
xx yy
xx yy
xx yy
where xx is ...
5
votes
1answer
219 views
dash: How to capture output of trap (invoked w/o arguments)?
The section on trap in the dash manpage states the following:
trap without any arguments cause it to write a list of signals and their associated action to the standard output in a format that is ...
3
votes
1answer
141 views
dash: List declared functions
What is the dash equivalent to bash's:
compgen -A function
which lists the names of the declared functions.
6
votes
2answers
281 views
dash: Pipe STDIN to multiple commands and their output to STDOUT in defined order
At first I thought this answer was the solution, but now I think I need a temporary file as buffer.
This works unreliably:
#!/bin/sh
echo 'OK' |
{
{
tee /dev/fd/3 | head --bytes=1 >&...
6
votes
1answer
2k views
Assign file name to a variable using pathname expansion
Is there a reliable way to assign a file name to a variable taking advantage of pathname expansion?
This works but looks kind of dodgy:
the_file="$(echo ~/downloads/stack-*-linux-x86_64-static.tar....
1
vote
3answers
3k views
Print variable with backslashes in dash
My shell is dash. My problem is the following:
# A="abc\nde fg"
# printf "$A"
abc
de fg#
# B="abc\\nde fg"
# printf "$B"
abc
de fg#
# C="abc\\\nde fg"
# printf "$C"
abc\nde fg#
The string ...
0
votes
2answers
1k views
Setting umask for su user command
In my system I set the umask for the user root to 0077 and for the non-root users to 0027 (via /etc/profile). This is working for the normal terminal logins. But if I login as root and change user ...
7
votes
2answers
251 views
Why does dash expand \\\\ differently to bash?
I have a little open source project that for various reasons I've tried to write in reasonably portable shell script. Its automated integration tests check that hostile characters in path expressions ...
12
votes
2answers
819 views
Separate namespaces for functions and variables in POSIX shells
In dash, functions and variables appear to live in separate namespaces:
fn(){
fn="hello world"
}
fn; echo "The value is $fn!" #prints: The value is hello world!
fn; echo "The value is $fn!" #...
11
votes
1answer
594 views
how to emulate Process substitution in Dash
In bash, I can use process substitution and treat output of a process as if it was a file saved on disk:
$ echo <(ls)
/dev/fd/63
$ ls -lAhF <(ls)
lr-x------ 1 root root 64 Sep 17 12:55 /dev/fd/...
1
vote
2answers
822 views
How to run a bash script from a sh(dash) script?
I have a sh (shebang #!/bin/sh) script (sh.sh) which invokes a bash (shebang #!/bin/bash) sub-script:
. "some-path/bash.sh"
In the bash script I have a declaration of an associative array: declare -...
2
votes
1answer
88 views
shell script echo text name in for looping multiple texts
I am trying to do this
text1="word1 word2 word3"
text2="word4 word5"
text1="word6 word7 word8"
for var in $text1 $text2 $text3
do
echo $var" in "(__?__)
done
expected output
word1 in text1
word2 ...
3
votes
1answer
500 views
Getting script's real absolute path in /bin/sh
I'm looking for a way to get the real absolute path to the current /bin/sh script. It should work for situations like this one:
/path/to/symlink/in/PATH/somescript
-> ../../Package/current/...
3
votes
2answers
153 views
Job control in dash
I don't understand the problem about which the standard shell in Debian (dash) complains:
test@debian:~$ sh
$ man ls
ctrl+Z
[1] + Stopped man ls
$ jobs
[1] + Stopped ...
4
votes
2answers
345 views
Why does bash 4.3 keep allocating memory in a script
Why does this shell script gradually consume more memory in bash? I’m not using any local variables and although the value of cpid is changing at every iteration because ls exits immediately, but it ...
2
votes
3answers
2k views
How can I access the history buffer in sh? (not in Bash)
Is there a command history in sh, for example how to access it, and as well, how to ensure it is clear?
To clarify shells here: let's say you've logged on to a non-Gui Linux system, and $SHELL is ...
0
votes
0answers
100 views
How to freeze the dash bar in Gnome 3?
I'm on a freshly installed Debian 8.3 (Gnome 3.14) and I can't find if it is possible to display the dash bar permanently (as a dock on Mac OS X). The dash is hiding automatically... This looks like a ...
4
votes
2answers
1k views
Running source command with -x for debugging
I am trying to understand how a shell script is working. The tutorial states that the script should be run as the following way:
source oe-init-build-env rpi-build
Usually when doing this kind of ...
0
votes
1answer
116 views
Dash print expanded commands
Running xtrace or set -x with Bash will print the expanded command:
$ bash -xc 'touch "alfa bravo"'
+ touch 'alfa bravo'
However Dash does not print the command that is actually run:
$ dash -xc '...
1
vote
1answer
347 views
Bash FUNCNAME equivalent in Dash
Bash can print the current function name:
$ bash -c 'g(){ echo $FUNCNAME; }; g'
g
However Dash cannot use FUNCNAME:
$ dash -c 'g(){ echo $FUNCNAME; }; g'
It is possible to access the current ...
0
votes
3answers
80 views
DASH scripting errors: I don't think I know how to set up variables correctly
#!/bin/sh
export $REG=0x000000
export $DONE=0x4A9FFF
while $REG -le $DONE
do
(($REG+1))
printf 'wm8280_reg get 0x'$REG'\r\n'
sleep 1
done
This leads to the errors:
./...
1
vote
1answer
27 views
swap windows with dash script
I have written a bunch of dash scripts that resize and move windows for better efficiency.
The structure is the following: i have a row of 8 windows that are stacked to the bottom of my screen, like ...
