Questions tagged [command-substitution]
Questions about shell command substitution (such as $(command) or `command`), its mechanism, correct syntax etc. Not to be confused with aliasing.
410 questions
1
vote
1
answer
42
views
Abort on command substitution error in argument [duplicate]
How can I prevent command substitution in arguments from silently swallowing errors?
#!/bin/sh
set -e
echo "Evaluating $(false) should abort."
echo "This line should not be executed.&...
- 113
0
votes
2
answers
144
views
Process sed capture group with a bash function before replacement: "sh: 1: <bash function>: not found"
So, I was playing around with this answer, when I found that neither
printf_stdin () {
read input
printf "$input"
}
sed "/lorem ipsum foobar/ {
s/'/'\"'\"'/g
s/\...
- 145
2
votes
1
answer
531
views
Using a literal asterisk (*) in a filename within command substitution in bash
how do you supply a literal asterisk * when specifying a filename to a command substitution in bash?
Consider the following directory:
host:/tmp/backtick-test# ls -l
total 0
-rw-r--r-- 1 root wheel ...
- 103
0
votes
2
answers
88
views
One-liner piping from find/xargs with paths including spaces
The following question likely does not relate specifically to Vim. I use a Vim example, as this is where I encounter the issue.
Working on Ubuntu, I often open multiple files in Vim using tab pages:
$ ...
- 266
1
vote
1
answer
141
views
Multiline command substitution - syntax errors with mysterious `+1`
I'm trying to break a long command substitution on to multiple lines, as discussed in this answer.
In a plain command pipeline, both explicit (\) and implicit line continuation work fine:
$ echo 'blah ...
- 532
0
votes
1
answer
76
views
command substitution and Dollar sign before variable
I have a file named fileWithOneCommand.txt with just one command as follows
ps -aux|head -n 5
then I write a testing shell script named 'test5.sh' with content as follow:
file=/home/somepath/...
- 133
0
votes
1
answer
51
views
Command substitution used with tput which doesn't print anything
I am doing a code-study of /lib/lsb/init-functions on mint 20 just to familiarise myself with SystemV init system.
There is log_action_end_msg function in it which has this code snippet,
TPUT=/usr/bin/...
- 193
-4
votes
1
answer
128
views
Why is command substitution resulting in 'command not found error'?
So doing
$(cat /etc/passwd)
results in "No such File or Directory"
and
"$(whereis cat)"
results in "command not found"
Why is command substitution not working in the ...
- 27
0
votes
1
answer
141
views
bash - check free available space against requered
in bash i will run a script that take a look in the folder folder123/ to know how much space is requered for the files they are in there.
but this requered value will i multiplie with 1,5 and than ...
- 539
1
vote
1
answer
103
views
How can I iterate over the white space separated words returned by a command substition?
I have the following simple shell command:
for x in $(echo one two three); do echo $x; done
When executed, it simply prints
one two three
on one line, i. e. the result of the command substitution is ...
- 2,321
0
votes
1
answer
96
views
Nested command substitution doesn't work, but hardcoded results work
I am trying to pass filenames retrieved from everything voidtools via their es.exe command line (it works similarly to mlocate) to an "image previewer" like gwenview or nsxiv (in wsl ...
- 381
0
votes
0
answers
50
views
Command Substitution doesn't work with spaces [duplicate]
I'm trying to pass a list of image files to open gwenview. The only way that seems to work is to list them on command line. However, some file paths have spaces, so they have to be additionally quoted....
- 381
0
votes
3
answers
136
views
Pass output of command line to awk variable
I am trying to normalise a data file using the number of lines in a previous version of the data file. After reading these questions, I thought this could work:
awk -v num=$(wc -l my_first_file.bed) '{...
- 245
0
votes
2
answers
110
views
Bash scripting: When to use variable, when function?
basic, innocent question:
In bash scripting, why ever using a function, if one can set a variable containing command substitution with the essence of the function - a certain command or set of ...
- 213
-1
votes
1
answer
163
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zgrep command not working correctly on command substitution [duplicate]
I am preparing a script
that will try to detect two texts on the same line.
This pattern is present in my application log files,
which then further used to identify which file contains the pattern.
...
