[PATCH] generic/397: be compatible with ignored SIGPIPE

[Eric Biggers <ebiggers3@gmail.com>]

From: Eric Biggers <ebiggers@google.com>

If generic/397 is executed in an environment with SIGPIPE ignored, it
fails because the 'yes' program prints an error message:

    yes: standard output: Broken pipe
    yes: write error

This can be reproduced with:

    trap '' SIGPIPE; ./check generic/397

Fix it by generating the string of 255 y's using just 'head' and 'tr'
instead of 'yes', 'head', and 'tr'.

Although it's not really a good idea to execute xfstests with SIGPIPE
ignored, this is the only test I've noticed where it causes a problem,
so it might as well be fixed in the test.

It would be much nicer to prevent this problem for all tests by making
the 'check' script restore the default SIGPIPE handler.  But that isn't
straightforward because bash's 'trap' builtin doesn't allow un-ignoring
signals that were ignored on entry to the shell.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 tests/generic/397 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/generic/397 b/tests/generic/397
index 7077d048..ba920891 100755
--- a/tests/generic/397
+++ b/tests/generic/397
@@ -69,7 +69,7 @@ for dir in $SCRATCH_MNT/edir $SCRATCH_MNT/ref_dir; do
 	touch $dir/empty > /dev/null
 	$XFS_IO_PROG -t -f -c "pwrite 0 4k" $dir/a > /dev/null
 	$XFS_IO_PROG -t -f -c "pwrite 0 33k" $dir/abcdefghijklmnopqrstuvwxyz > /dev/null
-	maxname=$(yes | head -255 | tr -d '\n') # 255 character filename
+	maxname=$(head -c 255 /dev/zero | tr '\0' y) # 255 character filename
 	$XFS_IO_PROG -t -f -c "pwrite 0 1k" $dir/$maxname > /dev/null
 	ln -s a $dir/symlink
 	ln -s abcdefghijklmnopqrstuvwxyz $dir/symlink2
-- 
2.13.1.508.gb3defc5cc-goog