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From: | Paul Eggert |
Subject: | bug#34488: Add sort --limit, or document workarounds for sort|head error messages |
Date: | Sun, 24 Feb 2019 10:33:47 -0800 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 |
The documentation should mention that SIGCHLD is special, in that --ignore-signal=CHLD might have no effect (POSIX says it's unspecified).
The documentation should say what happens if mutually-contradictory options are specified, e.g., '--default-signal=INT --ignore-signal=INT'. Presumably they are processed left-to-right, as is traditional for 'env' with contradictory operands.
There should be options --block-signal[=SIG], --unblock-signal[=SIG], and --setmask-signal[=SIG] that affect the signal mask, which is also inherited by the child. These can be implemented via pthread_sigmask.
The documentation should echo this suggestion in <http://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html>: "many existing applications wrongly assume that they start with certain signals set to the default action and/or unblocked.... Therefore, it is best not to block or ignore signals across execs without explicit reason to do so, and especially not to block signals across execs of arbitrary (not closely cooperating) programs."
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