151 questions
1
vote
1
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729
views
Portable way to check if an environment variable is set
In Bash you can check if an environment variable is set with test -v FOO. It doesn't work in Dash on Debian 11 though because its test doesn't support -v:
# test -v FOO
dash: 2: test: -v: unexpected ...
- 99k
1
vote
0
answers
47
views
how to get the Unix shell executable name for a script marked as executable and bin/bash shebang [duplicate]
I use the function getTrueShellExeName() posted by mklement0 at https://stackoverflow.com/a/23011530/7471760 in order to get the shell name of a script.
This works perfectly well in most cases, but I ...
- 850
0
votes
1
answer
79
views
Pass the entire content of the variable into a function
I need to convert the contents of the variables as they are into base64. I decided to make a function and pass the content of the variables into it and output it later. So far I have the following
#!/...
- 667
1
vote
3
answers
2k
views
How to understand syntax used in "while sleep 1000; do :; done" for dash?
I see this line of script from this tutorial on VS Code doc.
while sleep 1000; do :; done
I know the functionality of this line is to prevent process exiting. But I don't understand the syntax. Could ...
- 1,919
0
votes
1
answer
99
views
How do I pass command-line arguments to script executed from stdin
These work fine:
/bin/dash xyz.sh arg1
curl | /bin/dash -
Use case:
curl | sh - arg1
Ubuntu executes this as:
curl | /bin/dash - arg1
this fails with: sh: 0: Can't open arg1
How do I pass arg1 to ...
- 215
0
votes
0
answers
300
views
local marked function variables unavailable inside trap function - (d)ash shell
I've read that the local keyword introduces dynamic scoping, meaning the variable defined thus in a function will be visible until the function dies. Hence visible and changeable in other functions ...
- 3,840
1
vote
1
answer
116
views
How to use SED to find multiple paths in the same line and replace them with a different path?
I have a file with multiple paths in the same line:
cat modules.dep
kernel/mm/zsmalloc.ko:
kernel/crypto/lzo.ko:
kernel/drivers/char/tpm/tpm_vtpm_proxy.ko: kernel/drivers/char/tpm/tpm.ko
kernel/...
- 145
2
votes
1
answer
544
views
How to manipulate filenames with whitespace using IFS in dash shell?
I try to print and manipulate all filenames in current directory and there are some filenames containing whitespace. But when I use IFS=$'\n’ to delimite filenames, it also remove character "n&...
- 21
0
votes
1
answer
283
views
Why does "echo" ignore its first argument sometimes?
The output of this code seems to depend on the option I give (-n or -a) but I simply don't understand the reason.
Here's the portion of the code that doesn't work (just the code itself + outputs):
#!/...
- 5
2
votes
4
answers
1k
views
How can I multiply a character or string in native POSIX shell script?
This is not a duplicate of the other question for two reasons. That question did not specify that the answer had to be POSIX. The marked answer for that question does not run correctly in a Dash shell....
- 403
0
votes
1
answer
410
views
dash script, send yes for a command
I want to call a command with a script using dash. here is my code:
#!/bin/sh
ip='172.45.0.219'
cmd1='yes yes'
cmd2="./ssh foo@$ip"
eval $cmd1 | $cmd2
when I run my script this is my output:...
- 9
3
votes
1
answer
3k
views
"kill %1" fails and prints "No such process" inside script
I am currently using dash as main shell.
I tried to write a little function that should imitate wait, but with some text.
Here's a minimal, working code:
#!/bin/dash
wait() {
echo Waiting...
...
- 1,071
0
votes
1
answer
609
views
How to close a dd process that was started in a dash script with -SIGINT?
When I start a dd process directly from the Terminal with
dd if=/dev/zero of=/dev/null &
command, and send to it a -SIGINT with
kill -SIGINT <pid>
command, it closes successfully.
But when ...
- 445
0
votes
2
answers
389
views
Dash and C: eval "$(<cmdfile)" and system("eval \"\$(<cmdfile)\"") giving different results
I would like to use the system() function in C to evaluate an expression within a file cmdfile but I'm not getting the same results as when I do so on the command line directly. The content of cmdfile ...
- 630
0
votes
1
answer
551
views
Loop through a list of files with a specific MIME type in sh
I have a directory, and need to get a list of files with MIME types of application/pdf, which I can loop through and process with my CompressPdf function. The remaining files only need to be copied ...
- 683