Questions tagged [control-flow]
Control flow refers to the order that computer code is executed in when a program or script is running. Examples include loops (code is repeated) and conditionals where one branch is run instead of another. Use this tag for questions about control flow in scripts or programs – not questions about terminal flow control.
83 questions
7
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With `#!/bin/sh`, what is the closest to `;;&` (`bash`'s fallthrough)?
Without ;;&, /bin/sh gives Syntax error: ")" unexpected (expecting ";;").
;;& triggers shellcheck's ^-- SC2127 (error): To use cases with ;;&, specify #!/usr/bin/env ...
- 71
1
vote
3
answers
350
views
How to tail continuously a log file that is being deleted and recreated?
I need to extract information from a log file that is deleted and recreated every time a program runs. After detecting that the file exists (again), I would like to tail it for a certain regexp.
The ...
- 173
0
votes
1
answer
154
views
Is a newline equivalent to && in a bash script?
I'm very simply wondering if, in a bash script,
a new line is functionally 100% equivalent to &&?
e.g.:
#!/bin/bash
7z x "${file}"
mv "${file}" "${new_file}"
...
- 521
2
votes
4
answers
167
views
How to execute a command after the previous non-terminating command prints a certain string?
I want to execute commandA which prints the following:
line1
line2
line3
started successfully
line4
...
...
And when the line started successfully is printed I want to start another command (and ...
- 889
5
votes
3
answers
981
views
Tool to detect errors in application's execution logic
I want to detect errors in application's execution logic. E.g.:
forgot to call free() on address returned by malloc()
did not close file handle returned by open()
invalid flags passed to open()
...
- 1,022
0
votes
0
answers
29
views
How do I get this code to evaluate all arms of if-else? Why does Bash seem to interpret the characters that I input as integers? [duplicate]
The last elif arm does not get executed:
#!/usr/bin/bash
searches=("feet"
"axilas"
"lactant")
length=${#searches[@]}
searchFunction() {
echo "Enter the respective ...
- 23
0
votes
0
answers
15
views
my if statement is returning command not found [duplicate]
in my script
an if statement
returns:
line 3: []: command not found
the statement:
if ["$(pidof -x $(basename $0) -o %PPID)"]; then
echo process already running; exit;
fi
what I tried:
...
- 1
6
votes
1
answer
8k
views
if ! <command> (...) vs. <command> ; if [ $? -eq 0 ] (...)
I am working on a shell script and decided to check my work via shellcheck.net. I am able to get functionally the same behavior of the following two lines in my script:
findmnt /dev/sda1 >/dev/null ...
- 1,827
2
votes
1
answer
423
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Executing a remote script from a code repository causes endless loop
I often execute raw versions of remote Bash scripts in GitHub with this pattern:
wget -O - https://raw.githubusercontent.com/<username>/<project>/<branch>/<path>/<file> | ...
0
votes
1
answer
44
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Pausing script execution until user quits out of `less`
Goal: less the contents (from a variable) and then ask the user whether the contents should be saved to a file (i.e., .recovered_object) only after the user quits out of less.
The excerpt from my ...
- 13
0
votes
2
answers
338
views
How to modify and write to file before printing to STDERR
I am working on an automated pull request check via GitHub actions and I want to preserve some data from a command's stderr output between jobs.
For this, I need to write the stderr to an artifact ...
- 119
3
votes
5
answers
3k
views
How to achieve an early exit from a code block in a bash script (analogous to perl's `last` directive)?
One feature of Perl that I really like is its generalization of looping control keywords to any curly-brace-delimited lexical block1.
For example, one can use Perl's last directive to exit any such ...
- 16.4k
4
votes
2
answers
5k
views
Return "continue" from function called from loop
I'm currently refactoring a script which has slowly grown beyond control. I'm trying to spin off repetition into functions. However, I have a repeated test being called from a loop, and want it to ...
- 81
3
votes
2
answers
15k
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what is the use of script 2>/dev/null in the following script? [duplicate]
$!/bin/sh
if grep "$1" /etc/passwd 2>/dev/null #Search username at beging of line1
then
echo "Pattern found - Job Over"
else
echo "Pattern not found"
fi
7
votes
2
answers
1k
views
How to know the code flow of a driver module?
I am studying Linux device drivers, my main focus is on wifi drivers.
I want to know how the code flows when I plugin my device.
Maybe, I can do something like add a printk line in every function.
...
- 195