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author | Johannes Stoelp <johannes.stoelp@gmail.com> | 2024-08-20 01:03:48 +0200 |
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committer | Johannes Stoelp <johannes.stoelp@gmail.com> | 2024-08-20 01:04:22 +0200 |
commit | 88fc5bc98370066490a9670c6b28fba91efd7d4d (patch) | |
tree | 630ff0e49badd3f0c660b933a142c860beb1f679 /src | |
parent | 7ca41565c4e70b212cb88a4d18c18fa35768df6d (diff) | |
download | notes-88fc5bc98370066490a9670c6b28fba91efd7d4d.tar.gz notes-88fc5bc98370066490a9670c6b28fba91efd7d4d.zip |
zsh,bash: trap handling
Diffstat (limited to 'src')
-rw-r--r-- | src/shells/bash.md | 34 | ||||
-rw-r--r-- | src/shells/zsh.md | 35 |
2 files changed, 68 insertions, 1 deletions
diff --git a/src/shells/bash.md b/src/shells/bash.md index f27b3a2..fb511b8 100644 --- a/src/shells/bash.md +++ b/src/shells/bash.md @@ -133,6 +133,40 @@ v=abc ; ( v=foo; echo $v; ) ; echo $v # abc ``` +## Trap Handling + +```bash +trap "<CMDs>" <SIG>/EXIT + +# Show current trap handler. +trap -p +# List signal names. +trap -l +``` + +#### Example: Run handler only on error exit +```bash +trap 'test $? -ne 0 && echo "run exit trap"' EXIT + +# -> no print +exit 0 +# -> print +exit 1 +``` + +#### Example: Mutex in shell script +For example if a script is triggered in unsynchronized, we may want to ensure +that a single script instance runs. +```bash +# open file=LOCK with fd=100 +exec 100>LOCK +# take exclusive lock, wait maximal for 3600s +flock -w 3600 -x 100 || { echo "flock timeout"; exit 1; } + +# eg automatically release lock when script exits +trap "flock -u 100" EXIT +``` + ## Argument parsing with `getopts` The `getopts` builtin uses following global variables: diff --git a/src/shells/zsh.md b/src/shells/zsh.md index f702655..6be1967 100644 --- a/src/shells/zsh.md +++ b/src/shells/zsh.md @@ -238,6 +238,40 @@ if [[ $INPUT =~ $REGEX ]]; then fi ``` +## Trap Handling + +```zsh +trap "<CMDs>" <SIG>/EXIT + +# Show current trap handler. +trap -p +# List signal names. +trap -l +``` + +#### Example: Run handler only on error exit +```zsh +trap 'test $? -ne 0 && echo "run exit trap"' EXIT + +# -> no print +exit 0 +# -> print +exit 1 +``` + +#### Example: Mutex in shell script +For example if a script is triggered in unsynchronized, we may want to ensure +that a single script instance runs. +```zsh +# open file=LOCK with fd=100 +exec 100>LOCK +# take exclusive lock, wait maximal for 3600s +flock -w 3600 -x 100 || { echo "flock timeout"; exit 1; } + +# eg automatically release lock when script exits +trap "flock -u 100" EXIT +``` + ## Completion ### Installation @@ -366,6 +400,5 @@ Explanation: > - [zsh completion functions][zsh-comp-fn] > - [zsh completion utility functions][zsh-comp-utility-fn] - [zsh-comp-fn]: http://zsh.sourceforge.net/Doc/Release/Completion-System.html#Completion-Functions [zsh-comp-utility-fn]: https://github.com/zsh-users/zsh-completions/blob/master/zsh-completions-howto.org#utility-functions |