Add a --help option to getpcaps.

Browsing the debian bug tracker, I noted this:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=560260

the output of getpcaps has been ugly forever and since I've been
meaning to fix that I figured I'd add some optional arguments too:

Added: --help, --usage, --verbose, --ugly, --legacy

Example:

$ ./progs/getpcaps 1 --verbose 1 --ugly 1
1: =ep
Capabilities for '1': =ep
Capabilities for `1': =ep

Signed-off-by: Andrew G. Morgan <morgan@kernel.org>

1 files changed, 26 insertions, 5 deletions

diff --git a/progs/getpcaps.c b/progs/getpcaps.c
index 264dd00..497abcd 100644
--- a/progs/getpcaps.c
+++ b/progs/getpcaps.c
@@ -11,23 +11,28 @@
 #include <stdlib.h>
 #include <sys/capability.h>
 
-static void usage(void)
+static void usage(int exiter)
 {
     fprintf(stderr,
 "usage: getcaps <pid> [<pid> ...]\n\n"
 "  This program displays the capabilities on the queried process(es).\n"
 "  The capabilities are displayed in the cap_from_text(3) format.\n\n"
-"[Copyright (c) 1997-8,2007 Andrew G. Morgan  <morgan@kernel.org>]\n"
+"  Optional arguments:\n"
+"     --help or --usage     display this message.\n"
+"     --verbose             use a more verbose output format.\n"
+"     --ugly or --legacy    use the archaic legacy output format.\n\n"
+"[Copyright (c) 1997-8,2007,2019 Andrew G. Morgan  <morgan@kernel.org>]\n"
 	);
-    exit(1);
+    exit(exiter);
 }
 
 int main(int argc, char **argv)
 {
     int retval = 0;
+    int verbose = 0;
 
     if (argc < 2) {
-	usage();
+	usage(1);
     }
 
     for ( ++argv; --argc > 0; ++argv ) {
@@ -35,6 +40,16 @@ int main(int argc, char **argv)
 	int pid;
 	cap_t cap_d;
 
+	if (!strcmp(argv[0], "--help") || !strcmp(argv[0], "--usage")) {
+	    usage(0);
+	} else if (!strcmp(argv[0], "--verbose")) {
+	    verbose = 1;
+	    continue;
+	} else if (!strcmp(argv[0], "--ugly") || !strcmp(argv[0], "--legacy")) {
+	    verbose = 2;
+	    continue;
+	}
+
 	pid = atoi(argv[0]);
 
 	cap_d = cap_get_pid(pid);
@@ -45,7 +60,13 @@ int main(int argc, char **argv)
 		continue;
 	} else {
 	    char *result = cap_to_text(cap_d, &length);
-	    fprintf(stderr, "Capabilities for `%s': %s\n", *argv, result);
+	    if (verbose == 1) {
+		printf("Capabilities for '%s': %s\n", *argv, result);
+	    } else if (verbose == 2) {
+		fprintf(stderr, "Capabilities for `%s': %s\n", *argv, result);
+	    } else {
+		printf("%s: %s\n", *argv, result);
+	    }
 	    cap_free(result);
 	    result = NULL;
 	    cap_free(cap_d);