From: yuriyryabikov <22548029+kurok@users.noreply.github.com>
Date: Wed, 22 Apr 2026 11:46:13 +0000 (+0100)
Subject: lslocks: add --pager and --nopager options
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=2779bd9f6ab4e234a90186a70bb6cc00f520d38b;p=thirdparty%2Futil-linux.git

lslocks: add --pager and --nopager options

Signed-off-by: yuriyryabikov <22548029+kurok@users.noreply.github.com>
---

diff --git a/bash-completion/lslocks b/bash-completion/lslocks
index b2a617e71..cd6d95cb3 100644
--- a/bash-completion/lslocks
+++ b/bash-completion/lslocks
@@ -42,6 +42,8 @@ _lslocks_module()
 		--notruncate
 		--list-columns
 		--filter
+		--pager
+		--nopager
 		--help
 		--version
 	"
diff --git a/include/pager.h b/include/pager.h
index 8a2edb3ae..508879934 100644
--- a/include/pager.h
+++ b/include/pager.h
@@ -7,8 +7,18 @@
 #ifndef UTIL_LINUX_PAGER
 #define UTIL_LINUX_PAGER
 
+#include <stdbool.h>
+
+/* --pager / --nopager */
+enum ul_pagermode {
+	UL_PAGER_AUTO = 0,	/* unspecified by user; obey PAGER_ENABLE */
+	UL_PAGER_NEVER,		/* --nopager (or --json/--raw) */
+	UL_PAGER_ALWAYS		/* --pager */
+};
+
 void pager_open(void);
 void pager_open_header(int header_lines, int first_col_width);
 void pager_close(void);
+bool pager_is_enabled(enum ul_pagermode mode);
 
 #endif
diff --git a/lib/pager.c b/lib/pager.c
index 64a0a3a6b..180447c1b 100644
--- a/lib/pager.c
+++ b/lib/pager.c
@@ -26,6 +26,7 @@
 #include "strutils.h"
 #include "ttyutils.h"
 #include "pager.h"
+#include "env.h"
 
 static const char *pager_argv[] = { "sh", "-c", NULL, NULL };
 
@@ -356,6 +357,40 @@ void pager_close(void)
 	pager_caught_sigpipe = 0;
 }
 
+/* Decide whether the pager should run for the given @mode.
+ *
+ * UL_PAGER_ALWAYS and UL_PAGER_NEVER reflect an explicit user choice
+ * (--pager / --nopager) and are honored unconditionally.
+ *
+ * UL_PAGER_AUTO consults the PAGER_ENABLE environment variable (accepted
+ * values parsed by ul_strtobool()). PAGER_ENABLE is ignored when stdout
+ * is not a terminal, so pipelines like `lslocks | grep foo` do not spawn
+ * a pager. The variable is also suppressed in privileged (SUID/SGID)
+ * contexts via safe_getenv().
+ */
+bool pager_is_enabled(enum ul_pagermode mode)
+{
+	switch (mode) {
+	case UL_PAGER_ALWAYS:
+		return true;
+	case UL_PAGER_NEVER:
+		return false;
+	case UL_PAGER_AUTO: {
+		const char *s;
+		bool val;
+
+		if (!isatty(STDOUT_FILENO))
+			return false;
+		s = safe_getenv("PAGER_ENABLE");
+		if (!s || ul_strtobool(s, &val) != 0)
+			return false;
+		return val;
+	}
+	default:
+		return false;
+	}
+}
+
 #ifdef TEST_PROGRAM_PAGER
 
 #define MAX 255
diff --git a/misc-utils/Makemodule.am b/misc-utils/Makemodule.am
index 27abeb3ca..11b2f82ee 100644
--- a/misc-utils/Makemodule.am
+++ b/misc-utils/Makemodule.am
@@ -85,7 +85,7 @@ usrbin_exec_PROGRAMS += lslocks
 MANPAGES += misc-utils/lslocks.8
 dist_noinst_DATA += misc-utils/lslocks.8.adoc
 lslocks_LDADD = $(LDADD) libcommon.la libmount.la libsmartcols.la
-lslocks_SOURCES = misc-utils/lslocks.c
+lslocks_SOURCES = misc-utils/lslocks.c include/pager.h lib/pager.c
 lslocks_CFLAGS = $(AM_CFLAGS) -I$(ul_libmount_incdir) -I$(ul_libsmartcols_incdir)
 endif
 
diff --git a/misc-utils/lslocks.8.adoc b/misc-utils/lslocks.8.adoc
index 964ec08a8..69894c728 100644
--- a/misc-utils/lslocks.8.adoc
+++ b/misc-utils/lslocks.8.adoc
@@ -72,6 +72,16 @@ ____
  lslocks --filter 'TYPE != "POSIX" and MODE == "READ" and PATH =~ ".*\.qcow2"'
 ____
 
+*--pager*::
+Pipe output into a pager (by default *less*(1)). The pager freezes the
+header line so column names stay visible while scrolling.
+The *PAGER* environment variable overrides the default pager program.
+Mutually exclusive with *--json* and *--raw*.
+
+*--nopager*::
+Do not pipe output into a pager. Overrides the *PAGER_ENABLE* environment
+variable.
+
 *-r*, *--raw*::
 Use the raw output format.
 
@@ -87,6 +97,12 @@ include::man-common/env-smartcols.adoc[]
 *LSLOCKS_COLUMNS*=::
 Specify a comma-separated list of output columns to print. All columns listed by *--list-columns* can be used.
 
+*PAGER_ENABLE*=::
+If set to a recognized boolean value (e.g. "yes", "true", "on", "1"), automatically pipe output through a pager.
+The *--pager* and *--nopager* command-line options override this variable.
+Ignored when standard output is not a terminal, and in privileged (setuid/setgid) contexts.
+This is a project-independent variable; other tools may support it as well.
+
 == OUTPUT
 
 COMMAND::
diff --git a/misc-utils/lslocks.c b/misc-utils/lslocks.c
index 8d79af4d7..fbaf7a2f8 100644
--- a/misc-utils/lslocks.c
+++ b/misc-utils/lslocks.c
@@ -50,6 +50,7 @@
 #include "procfs.h"
 #include "column-list-table.h"
 #include "fileutils.h"
+#include "pager.h"
 
 /* column IDs */
 enum {
@@ -138,6 +139,7 @@ struct lslocks {
 	int raw;
 	int json;
 	int bytes;
+	enum ul_pagermode pager_mode;
 
 	pid_t target_pid;
 
@@ -947,6 +949,8 @@ static void __attribute__((__noreturn__)) usage(void)
 	fputs(_(" -Q, --filter <expr>    apply display filter\n"), out);
 	fputs(_(" -r, --raw              use the raw output format\n"), out);
 	fputs(_(" -u, --notruncate       don't truncate text in columns\n"), out);
+	fputs(_("     --pager            pipe output into a pager\n"), out);
+	fputs(_("     --nopager          disable pager output\n"), out);
 
 	fputs(USAGE_SEPARATOR, out);
 	fprintf(out, USAGE_LIST_COLUMNS_OPTION(24));
@@ -1081,7 +1085,9 @@ int main(int argc, char *argv[])
 	struct libscols_filter *filter = NULL;
 	char *outarg = NULL;
 	enum {
-		OPT_OUTPUT_ALL = CHAR_MAX + 1
+		OPT_OUTPUT_ALL = CHAR_MAX + 1,
+		OPT_PAGER,
+		OPT_NO_PAGER,
 	};
 	static const struct option long_opts[] = {
 		{ "bytes",      no_argument,       NULL, 'b' },
@@ -1097,11 +1103,16 @@ int main(int argc, char *argv[])
 		{ "noinaccessible", no_argument, NULL, 'i' },
 		{ "filter",     required_argument, NULL, 'Q' },
 		{ "list-columns", no_argument,     NULL, 'H' },
+		{ "pager",      no_argument,       NULL, OPT_PAGER },
+		{ "nopager",    no_argument,       NULL, OPT_NO_PAGER },
 		{ NULL, 0, NULL, 0 }
 	};
 
 	static const ul_excl_t excl[] = {	/* rows and cols in ASCII order */
 		{ 'J','r' },
+		{ 'J', OPT_PAGER },
+		{ 'r', OPT_PAGER },
+		{ OPT_PAGER, OPT_NO_PAGER },
 		{ 0 }
 	};
 	int excl_st[ARRAY_SIZE(excl)] = UL_EXCL_STATUS_INIT;
@@ -1127,6 +1138,7 @@ int main(int argc, char *argv[])
 			break;
 		case 'J':
 			lslocks.json = 1;
+			lslocks.pager_mode = UL_PAGER_NEVER;
 			break;
 		case 'p':
 			lslocks.target_pid = strtopid_or_err(optarg, _("invalid PID argument"));
@@ -1143,6 +1155,7 @@ int main(int argc, char *argv[])
 			break;
 		case 'r':
 			lslocks.raw = 1;
+			lslocks.pager_mode = UL_PAGER_NEVER;
 			break;
 		case 'u':
 			disable_columns_truncate();
@@ -1151,6 +1164,12 @@ int main(int argc, char *argv[])
 		case 'H':
 			collist = 1;
 			break;
+		case OPT_PAGER:
+			lslocks.pager_mode = UL_PAGER_ALWAYS;
+			break;
+		case OPT_NO_PAGER:
+			lslocks.pager_mode = UL_PAGER_NEVER;
+			break;
 		case 'Q':
 			filter = new_filter(optarg);
 			break;
@@ -1191,6 +1210,9 @@ int main(int argc, char *argv[])
 	if (filter)
 		init_scols_filter(table, filter, lslocks.bytes);
 
+	if (pager_is_enabled(lslocks.pager_mode))
+		pager_open_header(lslocks.no_headings ? 0 : 1, 0);
+
 	/* get_pids_locks() get locks related information from "lock:" fields
 	 * of /proc/$pid/fdinfo/$fd as fallback information.
 	 * get_proc_locks() used the fallback information if /proc/locks
@@ -1208,5 +1230,7 @@ int main(int argc, char *argv[])
 	scols_unref_table(table);
 
 	lslocks_free(&lslocks);
+
+	pager_close();
 	return rc;
 }
diff --git a/misc-utils/meson.build b/misc-utils/meson.build
index 4d95beadc..8bb99822e 100644
--- a/misc-utils/meson.build
+++ b/misc-utils/meson.build
@@ -45,7 +45,8 @@ whereis_manadocs = files('whereis.1.adoc')
 
 lslocks_sources = files(
   'lslocks.c',
-)
+) + \
+  pager_c
 lslocks_manadocs = files('lslocks.8.adoc')
 
 lsblk_sources = files(