Add support for set -o pipefail

With the pipefail option set, the exit status of a pipeline is 0 if all
commands succeed, or the return status of the rightmost command that
fails. This can help str

Add support for set -o pipefail

With the pipefail option set, the exit status of a pipeline is 0 if all
commands succeed, or the return status of the rightmost command that
fails. This can help stronger error checking, but is not a silver
bullet. For example, commands will exhibit a non-zero exit status if
they're killed by a SIGPIPE when writing to a pipe. Yet pipefail was
considered useful enough to be included in the next POSIX standard.

This implementation remembers the value of the pipefail option when
a pipeline is started, as described as option 1) in

https://www.austingroupbugs.net/view.php?id=789#c4102

Requested by ajacoutot@, ok millert@

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When system calls indicate an error they return -1, not some arbitrary
value < 0. errno is only updated in this case. Change all (most?)
callers of syscalls to follow this better, and let's see if

When system calls indicate an error they return -1, not some arbitrary
value < 0. errno is only updated in this case. Change all (most?)
callers of syscalls to follow this better, and let's see if this strictness
helps us in the future.

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Favor usage of __func__ in warning/error messages. Some of them referred to the
wrong function and fix the rest for consistency.
Diff from Michael W. Bombardieri with some cosmetic cleanup applied.

Favor usage of __func__ in warning/error messages. Some of them referred to the
wrong function and fix the rest for consistency.
Diff from Michael W. Bombardieri with some cosmetic cleanup applied.

ok benno@ tb@

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Introduce internal_warningf() and mark internal_errorf() as noreturn

This helps tools like scan-build, and follows the example of warningf()
and errorf(). ok anton@

update comments that were left behind in the recent unifdef JOB commit
from Klemens Nanni, thanks.

unifdef JOBS support

Prompted by a mail from Klemens Nanni, who also had the same diff.
ok deraadt@ millert@

Typos in comments: 'it' -> 'if' and 'noityf' -> 'notify'.

from Klemens Nanni

remove some ARGSUSED

rename global "e" to genv to avoid accidental shadowing and aliasing.
ok millert nicm tb

Move system headers from sh.h to those files that actually need them.

ok mmcc@ a while ago

use symbolics for flags to open
from Ricardo Mestre

Use isdigit() instead of ksh's homebrewed alternative.

ok nicm@. Also discussed with millert@ and guenther@.

Move string.h include from sh.h to the files that use it.

ok nicm@

Move limits.h include from sh.h to the files that actually need it. No
binary change.

ok nicm@

Apply style(9) to header includes.

ok nicm@

More (foo *)0 -> NULL, from Michael McConville. No binary change.

Remove unnecessary casts, from Michael McConville. No binary change.

correct spelling of NULL from (char *)0. from Michael McConville.
ok md5

stop abusing null (the variable) for an empty string in output formats.
from Michael McConville
ok nicm

Replace newline and space defines by "\n" and " " directly, from Michael
McConville. ok millert

Remove INT32 define and just use int, from Martijn van Duren and Michael
McConville. ok deraadt

Convert many atoi() calls to strtonum(), adding range checks and failure
handling along the way.
Reviews by Brendan MacDonell, Jeremy Devenport, florian, doug, millert

Add a proper suspend builtin that saves/restores the tty and pgrp
as needed instead of an alias that just sends SIGSTOP. Login shells
may be suspended if they are not running in an orphan process gr

Add a proper suspend builtin that saves/restores the tty and pgrp
as needed instead of an alias that just sends SIGSTOP. Login shells
may be suspended if they are not running in an orphan process group.
OK guenther@ jmc@

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remember to restore errno (ie. stop someone from making a mistake later)
ok guenther

a dangling do / while that was very very ugly