yes: avoid redundant diagnostics on write error

* src/yes.c (main): For large inputs only write a single
diagnostic for write errors.
* tests/misc/yes.sh: Test when /dev/full is available.

1 files changed, 16 insertions, 3 deletions

diff --git a/tests/misc/yes.sh b/tests/misc/yes.sh
index 137159334..a3027432b 100755
--- a/tests/misc/yes.sh
+++ b/tests/misc/yes.sh
@@ -30,9 +30,9 @@ for size in 1 1999 4095 4096 8191 8192 16383 16384; do
 done
 
 # Check the many small items case,
-# both fitting and overflowing the internal buffer
-external=env
-if external true $(seq 4000); then
+# both fitting and overflowing the internal buffer.
+# First check that 4000 arguments supported.
+if test 4000 -eq $(sh -c 'echo $#' 0 $(seq 4000)); then
   for i in 100 4000; do
     seq $i | paste -s -d ' ' | sed p > out.1
     yes $(seq $i) | head -n2 > out.2
@@ -40,4 +40,17 @@ if external true $(seq 4000); then
   done
 fi
 
+# Check a single appropriate diagnostic is output on write error
+if test -w /dev/full && test -c /dev/full; then
+  # The single output diagnostic expected,
+  # (without the possibly varying :strerror(ENOSPC) suffix).
+  printf '%s\n' "yes: standard output" > exp
+
+  for size in 1 16384; do
+    returns_ 1 yes "$(printf %${size}s '')" >/dev/full 2>errt
+    sed 's/\(yes:.*\):.*/\1/' errt > err
+    compare exp err || fail=1
+  done
+fi
+
 Exit $fail