Package: exim4
Version: 4.63-17
I set up a test program, piping into the following perl script:
$ cat junk/t.pl
#!/usr/bin/perl
print STDERR "Signal handling for SIGPIPE: $SIG{PIPE}.\n";
die;
$
When I tested this by putting
|/home/ian/junk/t.pl
in .forward and sending an email, the expected bounce contained the
following text:
The following text was generated during the delivery attempt:
------ pipe to |/home/ian/junk/t.pl
generated by i...@liberator.relativity.greenend.org.uk ------
Signal handling for SIGPIPE: IGNORE.
Died at /home/ian/junk/t.pl line 3.
On UN*X all programs are entitled to assume that they inherit SIGPIPE
(and most other signals) set to SIG_DFL. Programs with careful error
handling can fail when SIGPIPE is set to SIG_IGN, because it causes
programs such as "cat" to do this:
$ sh -xc 'trap "" PIPE; (sleep 1; echo hi) | cat | true;
echo ${PIPESTATUS[*]}'
+ trap '' PIPE
+ sleep 1
+ cat
+ true
+ echo hi
cat: write error: Broken pipe
+ echo 0 1 0
0 1 0
$
Rather than this:
$ sh -xc '(sleep 1; echo hi) | cat | true; echo
${PIPESTATUS[*]}'
+ sleep 1
+ cat
+ true
+ echo hi
+ echo 0 141 0
0 141 0
$
Ian.
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