Collin Funk <[email protected]> writes:
> However, that means that when POSIXLY_CORRECT is not defined the exit
> status is ambiguous as shown in the following example:
>
> # Input with a cycle.
> $ printf 'a b\nb a\n' | ./src/tsort
> tsort: -: input contains a loop:
> tsort: a
> tsort: b
> a
> b
> $ echo $?
> 1
> # Program error.
> $ echo 'a a' | ./src/tsort > /dev/full
> tsort: write error: No space left on device
> $ echo $?
> 1
Oops, slight mistake in that example. Pretend that './src/tail' was
given the -w argument. The output and exit status will be the same.
Here it is run with POSIXLY_CORRECT set:
$ printf 'a b\nb a\n' | POSIXLY_CORRECT=1 ./src/tsort -w
tsort: -: input contains a loop:
tsort: a
tsort: b
a
b
$ echo $?
1
$ echo 'a a' | POSIXLY_CORRECT=1 ./src/tsort > /dev/full
tsort: write error: No space left on device
$ echo $?
125
We can use the exit value to determine the number of cycles (0 - 124) or
an error (125) in this case.
Collin
