Hi,
[Note: I'm not on the list, so put [email protected] in cc: if I need to
reply. thanx, Peter]
Feature request:
implement set -o pipefail. This will allow the user to request the
return code to be the one of the first pipe command with a non-zero
error.
The lack of which can be quite painful in scripting, even if a
bourne-shell/posix subset would otherwise be quite sufficient.
Advantages:
This allows use of pipes with proper error detection, which is quite
helpful for init scripts / cron or generally administration-style
scripts which exec shell commands from shell/perl/python/... scripts.
Usage case:
have a command like mv -i act on user input, while keeping output
(stdout+err) in a log AND returning mv's error code (or tee's if mv is
ok). in a perl script, this would be something like:
system "set -o pipefail; mv -i foo bar </dev/tty 2>&1 | tee -a LOG";
Part of the problem is that the shell used for open/system is often
hard-coded in the interpreter to be /bin/sh.
Work aound:
1. as root:
restore /bin/sh to point to a more complete shell of bourne-ancestry.
With the subsequent larger set of library dependencies, ...
or
2. non-root:
first detect a suitable shell:
# detect likely shells in path and /etc/shells
# for each shell, try $tmp=`set -o pipefail 2>&1`
# choose one that doesn't set a non-zero errror in $?.
# if all else fails, try defaulting to bash or ksh
system $shell, "-c",
'set -o pipefail; mv -i "$@" </dev/tty 2>&1 | tee -a LOG',
"world's most painful trivial system command",
"foo", "bar";
btw, wrappers like script might help, besides being a pain wrt LOG
management. But there's the slight of script -c false returning true.
Which makes e.g. script impossible to use.
--
cu
Peter
[email protected]
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