This increases throughput on systems with unlocked stdio functions.
E.g., 2.5x in the following case:
$ timeout 1m taskset 1 shuf -r -i 0-100 \
| taskset 2 uniq -c \
| taskset 3 pv -r > /dev/null
[ 100MiB/s]
$ timeout 1m taskset 1 shuf -r -i 0-100 \
| taskset 2 uniq -c \
| taskset 3 pv -r > /dev/null
[ 246MiB/s]
* src/uniq.c: Include assure.h.
(writeline): Convert the value to a string by hand and use fwrite, which
may be unlocked, instead of printf.
* tests/uniq/uniq-c-width.sh: New test to verify the padding logic.
* tests/local.mk (all_tests): Add the test case.
* NEWS: Mention the improvement.
---
NEWS | 4 ++++
src/uniq.c | 19 ++++++++++++++++++-
tests/local.mk | 1 +
tests/uniq/uniq-c-width.sh | 33 +++++++++++++++++++++++++++++++++
4 files changed, 56 insertions(+), 1 deletion(-)
create mode 100755 tests/uniq/uniq-c-width.sh
diff --git a/NEWS b/NEWS
index 613bda0a2..2ae329509 100644
--- a/NEWS
+++ b/NEWS
@@ -59,6 +59,10 @@ GNU coreutils NEWS -*-
outline -*-
'sort' will now better use available memory and parallel operation
when reading from unknown sized inputs like pipes.
+ 'uniq -c' now operates up to 2.5x times faster on systems with unlocked stdio
+ functions.
+
+
** Build-related
configure no longer accepts the --with-linux-crypto option, which allowed
diff --git a/src/uniq.c b/src/uniq.c
index 5834596f9..f91c4212c 100644
--- a/src/uniq.c
+++ b/src/uniq.c
@@ -23,6 +23,7 @@
#include "system.h"
#include "argmatch.h"
+#include "assure.h"
#include "linebuffer.h"
#include "fadvise.h"
#include "mcel.h"
@@ -324,7 +325,23 @@ writeline (struct linebuffer const *line,
return;
if (count_occurrences)
- printf ("%7jd ", linecount + 1);
+ {
+ char buf[7 + INT_BUFSIZE_BOUND (intmax_t)];
+ char *end = buf + sizeof buf;
+ char *p = end;
+ *--p = ' ';
+ intmax_t i = linecount + 1;
+ affirm (0 < i);
+ do
+ *--p = '0' + i % 10;
+ while ((i /= 10));
+ /* 7 characters, padded with spaces if LINECOUNT + 1 is too small. */
+ while (end - p < 8)
+ *--p = ' ';
+ const idx_t nbytes = end - p;
+ if (fwrite (p, sizeof (char), nbytes, stdout) != nbytes)
+ write_error ();
+ }
if (fwrite (line->buffer, sizeof (char), line->length, stdout)
!= line->length)
diff --git a/tests/local.mk b/tests/local.mk
index 154b591ce..0001534ac 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -531,6 +531,7 @@ all_tests = \
tests/uniq/uniq.pl \
tests/uniq/uniq-perf.sh \
tests/uniq/uniq-collate.sh \
+ tests/uniq/uniq-c-width.sh \
tests/misc/xattr.sh \
tests/misc/yes.sh \
tests/tail/wait.sh \
diff --git a/tests/uniq/uniq-c-width.sh b/tests/uniq/uniq-c-width.sh
new file mode 100755
index 000000000..27f8eef0a
--- /dev/null
+++ b/tests/uniq/uniq-c-width.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+# Test 'uniq -c' with various integer widths.
+
+# Copyright (C) 2026 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ uniq
+expensive_
+
+count=$(shuf -i 10000000-99999999 -n 1) || framework_failure_
+
+while test $count -gt 0; do
+ printf '%7d y\n' $count >exp || framework_failure_
+ yes | head -n $count | uniq -c >out 2>err || fail=1
+ compare exp out || fail=1
+ compare /dev/null err || fail=1
+ count=$((count / 10))
+done
+
+Exit $fail
--
2.54.0
