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Tags:
bash
debugging
output
Link:
🔍 See Original Question on Ask Ubuntu ⧉ 🔗
URL:
https://askubuntu.com/q/1147775
Title:
What does shellcheck warning SC2129 “Consider using { cmd1; cmd2; } >> file instead of individual redirects.” mean?
ID:
/2019/06/01/What-does-shellcheck-warning-SC2129-“Consider-using-_-cmd1_-cmd2_-_-__-file-instead-of-individual-redirects.”-mean_
Created:
June 1, 2019
Edited: June 12, 2020
Upload:
September 15, 2024
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I have this shellcheck warning I can’t figure out:
In /mnt/e/bin/iconic line 540:
printf "FALSE|" >> "$IconsRaw" # Select field number 1
^-- SC2129: Consider using { cmd1; cmd2; } >> file instead of individual redirects.
I’ve noticed many of us here use shellcheck to fix our bash scripts / shell commands so I hope the question is on topic.
As per comments posting relevant section of bash script:
if [[ "$X" == "?" || "$Y" == "?" ]] ; then
: # Bad X or Y offset usually "Link to Name.ext~" (backup name)
else
let i++
printf "FALSE|" >> "$IconsRaw" # Select field number 1
printf "%s|" "$i" >> "$IconsRaw" # 2
printf "%s|" "${File##*/}" >> "$IconsRaw"
printf "%s|" "$Linkless" >> "$IconsRaw" # 4
printf "%s|" "$Date" >> "$IconsRaw" # 5
printf "%s|" "$X" >> "$IconsRaw" # 6
echo "$Y" >> "$IconsRaw" # 7
fi
Solution
Thanks to accepted answer and comments I’ve learned that shellcheck not only catches errors in your code, but also suggests performance improvements. In this case the filename $IconsRaw was being opened and closed many times with each printf and echo.
The more efficient bash code:
# X,Y screen coordinates invalid on backup files ending with "~"
! [[ "$X" == "?" || "$Y" == "?" ]] && { let i++; echo \
"FALSE|$i|${File##*/}|$Linkless|$Date|$X|$Y" >> "$IconsRaw"; }