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New options to set signal handlers for the command being executed. --block-signal suggested by Paul Eggert in http://bugs.gnu.org/34488#71 --default-signal is useful to overcome the POSIX limitation that shell must not override inherited signal state, e.g. the second 'trap' here is a no-op: trap '' PIPE && sh -c 'trap - PIPE ; seq inf | head -n1' Instead use: trap '' PIPE && sh -c 'env --default-signal=PIPE seq inf | head -n1' Similarly, the following will prevent CTRL-C from terminating the program: env --ignore-signal=INT seq inf > /dev/null See https://bugs.gnu.org/34488#8 * NEWS: Mention new options. * doc/coreutils.texi (env invocation): Document new options. * man/env.x: Add example of --default-signal=SIG usage. (SEE ALSO): Mention sigprocmask. * src/env.c (signals): New global variable. (longopts): Add new options. (usage): Print new options. (parse_signal_params): Parse comma-separated list of signals, store in signals variable. (reset_signal_handlers): Set each signal to SIG_DFL/SIG_IGN. (parse_block_signal_params): Parse command-line options. (set_signal_proc_mask): Call sigprocmask to block/unblock signals. (main): Process new options. * src/local.mk (src_env_SOURCES): Add operand2sig.c. * tests/misc/env-signal-handler.sh: New test. * tests/local.mk (all_tests): Add new test.
68 lines
1.7 KiB
Plaintext
68 lines
1.7 KiB
Plaintext
'\" Copyright (C) 1998-2019 Free Software Foundation, Inc.
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'\"
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'\" This is free software. You may redistribute copies of it under the terms
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'\" of the GNU General Public License <https://www.gnu.org/licenses/gpl.html>.
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'\" There is NO WARRANTY, to the extent permitted by law.
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[NAME]
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env \- run a program in a modified environment
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[DESCRIPTION]
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.\" Add any additional description here
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[OPTIONS]
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.SS "\-S/\-\-split\-string usage in scripts"
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The
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.B \-S
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option allows specifying multiple parameters in a script.
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Running a script named
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.B 1.pl
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containing the following first line:
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.PP
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.RS
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.nf
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#!/usr/bin/env \-S perl \-w \-T
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\&...
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.fi
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.RE
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.PP
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Will execute
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.B "perl \-w \-T 1.pl".
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.PP
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Without the
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.B '\-S'
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parameter the script will likely fail with:
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.PP
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.RS
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.nf
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/usr/bin/env: 'perl \-w \-T': No such file or directory
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.fi
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.RE
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.PP
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See the full documentation for more details.
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.PP
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.SS "\-\-default-signal[=SIG]" usage
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This option allows setting a signal handler to its default
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action, which is not possible using the traditional shell
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trap command. The following example ensures that seq
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will be terminated by SIGPIPE no matter how this signal
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is being handled in the process invoking the command.
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.PP
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.RS
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.nf
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sh \-c 'env \-\-default-signal=PIPE seq inf | head \-n1'
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.fi
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.RE
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.PP
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[NOTES]
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POSIX's exec(2) pages says:
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.RS
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"many existing applications wrongly assume that they start with certain
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signals set to the default action and/or unblocked.... Therefore, it is best
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not to block or ignore signals across execs without explicit reason to do so,
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and especially not to block signals across execs of arbitrary (not closely
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cooperating) programs."
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.RE
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[SEE ALSO]
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sigaction(2), sigprocmask(2), signal(7)
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