From c5cb541299dc9399d32b769d6c88ee5643428d3e Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Thu, 23 Mar 2017 14:27:42 +0100
Subject: [PATCH] fincore: add --output

Signed-off-by: Karel Zak <kzak@redhat.com>
---
 misc-utils/fincore.1 | 12 ++++++++++++
 misc-utils/fincore.c | 25 +++++++++++++++++++++----
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/misc-utils/fincore.1 b/misc-utils/fincore.1
index c32d6312e..a615d6ab6 100644
--- a/misc-utils/fincore.1
+++ b/misc-utils/fincore.1
@@ -16,6 +16,13 @@ pages in core, a file size, and a file name.  If an error
 occurs during counting, then an error message is printed to the stderr and
 .B fincore
 continues processing the rest of files listed in a command line.
+
+The default output is subject to change.  So whenever possible, you should
+avoid using default outputs in your scripts.  Always explicitly define expected
+columns by using
+.B \-\-output
+.I columns-list
+in environments where a stable output is required.
 .SH OPTIONS
 .TP
 .BR \-n , " \-\-noheadings"
@@ -24,6 +31,11 @@ Do not print a header line in status output.
 .BR \-b , " \-\-bytes"
 Print the SIZE column in bytes rather than in a human-readable format.
 .TP
+.BR \-o , " \-\-output \fIlist\fP"
+Define output columns.  See the \fB\-\-help\fP output to get a list of the
+currently supported columns. The default list of columns may be extended if \fIlist\fP is
+specified in the format \fI+list\fP.
+.TP
 \fB\-V\fR, \fB\-\-version\fR
 Display version information and exit.
 .TP
diff --git a/misc-utils/fincore.c b/misc-utils/fincore.c
index f7bccdf62..2d46fae39 100644
--- a/misc-utils/fincore.c
+++ b/misc-utils/fincore.c
@@ -239,17 +239,25 @@ static int fincore_name(struct fincore_control *ctl,
 
 static void __attribute__((__noreturn__)) usage(FILE *out)
 {
+	size_t i;
+
 	fputs(USAGE_HEADER, out);
 	fprintf(out, _(" %s [options] file...\n"), program_invocation_short_name);
 
 	fputs(USAGE_OPTIONS, out);
-	fputs(_(" -b, --bytes               print sizes in bytes rather than in human readable format\n"), out);
-	fputs(_(" -n, --noheadings          don't print headings\n"), out);
+	fputs(_(" -b, --bytes           print sizes in bytes rather than in human readable format\n"), out);
+	fputs(_(" -n, --noheadings      don't print headings\n"), out);
+	fputs(_(" -o, --output <list>   output columns\n"), out);
 
 	fputs(USAGE_SEPARATOR, out);
 	fputs(USAGE_HELP, out);
 	fputs(USAGE_VERSION, out);
 
+	fprintf(out, _("\nAvailable columns (for --output):\n"));
+
+	for (i = 0; i < ARRAY_SIZE(infos); i++)
+		fprintf(out, " %11s  %s\n", infos[i].name, _(infos[i].help));
+
 	fprintf(out, USAGE_MAN_TAIL("fincore(1)"));
 
 	exit(out == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
@@ -260,14 +268,16 @@ int main(int argc, char ** argv)
 	int c;
 	size_t i;
 	int rc = EXIT_SUCCESS;
+	char *outarg = NULL;
 
 	struct fincore_control ctl = {
-			.pagesize = getpagesize()
+		.pagesize = getpagesize()
 	};
 
 	static const struct option longopts[] = {
 		{ "bytes",      no_argument, NULL, 'b' },
 		{ "noheadings", no_argument, NULL, 'n' },
+		{ "output",     required_argument, NULL, 'o' },
 		{ "version",    no_argument, NULL, 'V' },
 		{ "help",	no_argument, NULL, 'h' },
 		{ NULL, 0, NULL, 0 },
@@ -278,7 +288,7 @@ int main(int argc, char ** argv)
 	textdomain(PACKAGE);
 	atexit(close_stdout);
 
-	while ((c = getopt_long (argc, argv, "bnVh", longopts, NULL)) != -1) {
+	while ((c = getopt_long (argc, argv, "bno:Vh", longopts, NULL)) != -1) {
 		switch (c) {
 		case 'b':
 			ctl.bytes = 1;
@@ -286,6 +296,9 @@ int main(int argc, char ** argv)
 		case 'n':
 			ctl.noheadings = 1;
 			break;
+		case 'o':
+			outarg = optarg;
+			break;
 		case 'V':
 			printf(UTIL_LINUX_VERSION);
 			return EXIT_SUCCESS;
@@ -307,6 +320,10 @@ int main(int argc, char ** argv)
 		columns[ncolumns++] = COL_FILE;
 	}
 
+	if (outarg && string_add_to_idarray(outarg, columns, ARRAY_SIZE(columns),
+					 &ncolumns, column_name_to_id) < 0)
+		return EXIT_FAILURE;
+
 	scols_init_debug(0);
 	ctl.tb = scols_new_table();
 	if (!ctl.tb)