pipe - Bash: Is trap while piping work as expected? -
here minimal code issue demonstration: http://pastebin.com/5txdpsh5
#!/bin/bash set -e set -o pipefail function echotraps() { echo "= on start:" trap -p trap -- 'echo func-exit' exit echo "= after set new:" trap -p # can ensure after script done - file '/tmp/tmp.txt' not created trap -- 'echo sig 1>/tmp/tmp.txt' sigpipe sighup sigint sigquit sigterm } trap -- 'echo main-exit1' exit echo "===== subshell trap" ( echotraps; ) echo "===== pipe trap" echotraps | cat echo "===== done everything" output
===== subshell trap = on start: = after set new: trap -- 'echo func-exit' exit func-exit ===== pipe trap = on start: = after set new: trap -- 'echo func-exit' exit ===== done main-exit1 expected output
===== subshell trap = on start: = after set new: trap -- 'echo func-exit' exit func-exit ===== pipe trap = on start: = after set new: trap -- 'echo func-exit' exit func-exit <---- here expected difference ===== done main-exit1 nb: tested osx 10.9.2 bash (3.2.51) - other versions of bash has same difference between actual expected output, , described bellow
here more test cases amusement:
$ cat traps.sh #!/bin/bash echotraps() { echo "entering echotraps()" printf " traps: %s\n" "$(trap -p)" echo " setting trap" trap -- 'echo "func-exit()"' exit printf " traps: %s\n" "$(trap -p)" echo "exiting echotraps()" } trap -- 'echo "main-exit()"' exit echo "===== calling '( echotraps; )'" ( echotraps; ) echo echo "===== calling 'echotraps | cat'" echotraps | cat echo echo "===== calling '( echotraps; ) | cat'" ( echotraps; ) | cat echo echo "===== calling '{ echotraps; } | cat'" { echotraps; } | cat echo bash-4.2.25(1)
$ ./traps.sh ===== calling '( echotraps; )' entering echotraps() traps: setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() func-exit() ===== calling 'echotraps | cat' entering echotraps() traps: trap -- 'echo "main-exit()"' exit setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() ===== calling '( echotraps; ) | cat' entering echotraps() traps: setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() func-exit() ===== calling '{ echotraps; } | cat' entering echotraps() traps: trap -- 'echo "main-exit()"' exit setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() main-exit() bash-4.3.0(1)
$ bash-static-4.3.2/bin/bash-static traps.sh ===== calling '( echotraps; )' entering echotraps() traps: setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() func-exit() ===== calling 'echotraps | cat' entering echotraps() traps: trap -- 'echo "main-exit()"' exit setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() ===== calling '( echotraps; ) | cat' entering echotraps() traps: setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() func-exit() ===== calling '{ echotraps; } | cat' entering echotraps() traps: trap -- 'echo "main-exit()"' exit setting trap traps: trap -- 'echo "func-exit()"' exit exiting echotraps() func-exit() main-exit() bottom line: don't rely on edge-cases this. remember investigating other inconsistencies (not traps) regards subshells , pipes , tried wrap head around bash source code , don't want go down route , try understand why behaves in situations (the code horrible, btw). can see, things seem have been "fixed" and/but both examples behave differently yours.
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