Questions tagged [shell]
The shell is Unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …). For shell scripts with errors, please check them in http://shellcheck.net before posting here.
12,136
questions
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What's the difference between "ps > log" and "log < ps" in GNU Bash shell? [duplicate]
Why is that in the command "log > ps" the shell considers "ps" as a file?
Does these operators (> and <) behave differently in other shells aside GNU Bash?
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-1
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0
answers
18
views
Why "read var 1< file1" does not read from file in GNU Bash shell? And why "read var < file1" does? [duplicate]
If the number 1 means stdout, why I'm not reading the stdout from file in "1< file" ?
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3
votes
1
answer
136
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How to overload / customize bash (or any other shell) commands handler?
When in bash some non existing command is run, corresponding error message appears:
$ non-existent-command
non-existent-command: command not found
Is it possible to customize this behavior?
I would ...
- 245
2
votes
1
answer
38
views
What does POSIX's third exception to the application of `set -e` mean?
The POSIX shell standard gives three exceptions to the application of set -e:
The failure of any individual command in a multi-command pipeline shall not cause the shell to exit. Only the failure of ...
- 51
0
votes
0
answers
7
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Autocomplection with description in zsh
General overview
This question complete this other one.
I try to set an autocomplete for --test parameter who should suggest a list of possible values (Here “foo” and “bar”). Until theire, it pretty ...
- 1,290
-1
votes
1
answer
34
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Is the idea of having a login shell and a non-login shell merely a way of making user preferences? [duplicate]
Scouring the internet about the difference between a login shell and a non-login shell, it turns out that the ultimate difference is merely the files that are being sourced. A login shell sources some ...
- 317
3
votes
2
answers
344
views
"history" command ordered by most common
Can I get the output of history sorted in order of most-used?
I know how to do it in a programming language, but not from the shell. In my case I'm on macOS with zsh.
I know I could use uniq and sort ...
- 414
0
votes
5
answers
108
views
What is the difference between using code $variable and ${variable}2?
What is the difference between using code $variable and ${variable}2 ?
Example:
file ='GLOBAL_AR_COLLECTOR_COMMENTS20240614ALYSSAB.TXT'
prefix ='GLOBAL_AR_COLLECTOR_COMMENTS'
In my shell script code ...
3
votes
1
answer
446
views
What is the precedence of operators '=', '||'
In this command, if curl succeeds, then res will be set to the output of curl. It seems = has higher precedence than ||.
res=$(curl -s "http://example.com")||true
But || should have higher ...
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1
vote
1
answer
28
views
omz reload in zsh widget
I am using zsh+oh-my-zsh and I am using the following code to change .zshrc using a hotkey and I am trying to reload omz after the change:
function f() {
# ... update .zshrc here ...
omz reload
}
...
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1
vote
1
answer
20
views
zsh autocompletion for parametre value
General overview
Here is my auto complexion file:
_triumphum_complete() {
_arguments \
'(- 1 *)'{-h,--help}'[show help options]' \
'(- 1 *)--tui[Run the game selection interface]' \
'(- 1 *)'{-r,...
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votes
0
answers
48
views
What is the output of the following ROT13 transformation command? [closed]
The command I'm using is:
echo "YRNEAVAT_YVAHK_SHAQNZRAGNYF" | tr '[A-Z]' '[N-ZA-M]'
I'm having trouble figuring out the exact output of this command.
Could someone explain the process and ...
7
votes
3
answers
675
views
Is there an equivalent of caniuse for commands on posix systems?
I'm thinking about using a callout to the jq command in a utility script I'm writing, rather than parsing JSON manually.
In order to make the script as portable as possible, I want to know which ...
0
votes
1
answer
37
views
Get a list of all user's commands from a non-interactive shell
I am writing a script that would automatically suggest some new aliases/functions to be added to a user's shell config. Before doing that, however, I would like to make sure the aliases being ...
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1
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70
views
How to convert multiple columns to rows in shell (unpivoting)
I have a tab separated table with hundreds of columns and rows, like that:
OTUId AC0184 AC0250 AC0257 AC0258 AC0262 AC0263 AC0289 AC0293
OTU549024624 51659 0 0 0 0 0 0 0
OTU565712448 108 0 0 0 0 0 0 0 ...
