Bring Barry Morris' changes from FreeBSD 1.1.5.1 back: pass arguments

to the target login's shell.  This allows for "su -c".

Do it right this time and also explain this behaviour in the man
page. :)

Obtained from:	bsm's work in FreeBSD 1.1.5.1

2 files changed, 50 insertions, 9 deletions

diff --git a/usr.bin/su/su.1 b/usr.bin/su/su.1
index ea9edcf..d4abfd0 100644
--- a/usr.bin/su/su.1
+++ b/usr.bin/su/su.1
@@ -31,6 +31,7 @@
 .\"
 .\"	@(#)su.1	8.2 (Berkeley) 4/18/94
 .\"
+.\" this is for hilit19's braindeadness: "
 .Dd April 18, 1994
 .Dt SU 1
 .Os
@@ -40,7 +41,7 @@
 .Sh SYNOPSIS
 .Nm su
 .Op Fl Kflm
-.Op Ar login
+.Op Ar login Op Ar args
 .Sh DESCRIPTION
 .Nm Su
 requests the Kerberos password for
@@ -128,6 +129,17 @@ and
 options are mutually exclusive; the last one specified
 overrides any previous ones.
 .Pp
+If the optional
+.Ar args
+are provided on the command line, they are passed to the login shell of
+the target login.  This allows it to pass arbitrary commands via
+the
+.Fl c
+option as understood by most shells.  Note that
+.Fl c
+usually expects a single argument only; you have to quote it when
+passing multiple words.
+.Pp
 Only users in group 0 (normally
 .Dq wheel )
 can
@@ -165,6 +177,21 @@ The user ID is always the effective ID (the target user ID) after an
 .Nm su
 unless the user ID is 0 (root).
 .El
+.Sh EXAMPLES
+.Bl -tag -width 5n -compact
+.It Li "su man -c catman"
+Runs the command
+.Li catman
+as user
+.Li man .
+You will be asked for man's password unless your real UID is 0.
+.It Li "su man -c 'catman /usr/share/man /usr/local/man /usr/X11R6/man'"
+Same as above, but the target command constitutes of more than a
+single word.
+.It Li "su -l foo"
+Pretend a login for user
+.Li foo .
+.El
 .Sh HISTORY
 A
 .Nm
diff --git a/usr.bin/su/su.c b/usr.bin/su/su.c
index b3eb587..e8afb37 100644
--- a/usr.bin/su/su.c
+++ b/usr.bin/su/su.c
@@ -86,20 +86,20 @@ main(argc, argv)
 	char *targetpass;
 	int iswheelsu;
 #endif /* WHEELSU */
-	char *p, **g, *user, *shell, *username, *cleanenv[20], *nargv[4], **np;
+	char *p, **g, *user, *shell, *username, *cleanenv[20], **nargv, **np;
 	struct group *gr;
 	uid_t ruid;
-	int asme, ch, asthem, fastlogin, prio;
+	int asme, ch, asthem, fastlogin, prio, i;
 	enum { UNSET, YES, NO } iscsh = UNSET;
 	char shellbuf[MAXPATHLEN];
 
-	np = &nargv[3];
-	*np-- = NULL;
 #ifdef WHEELSU
 	iswheelsu =
 #endif /* WHEELSU */
 	asme = asthem = fastlogin = 0;
-	while ((ch = getopt(argc, argv, ARGSTR)) != EOF)
+	user = "root";
+	while(optind < argc)
+	    if((ch = getopt(argc, argv, ARGSTR)) != EOF)
 		switch((char)ch) {
 #ifdef KERBEROS
 		case 'K':
@@ -121,9 +121,24 @@ main(argc, argv)
 		case '?':
 		default:
 			(void)fprintf(stderr, "usage: su [%s] [login]\n",
-			    ARGSTR);
+				      ARGSTR);
 			exit(1);
-		}
+		      }
+	    else
+	    {
+		user = argv[optind++];
+		break;
+	    }
+
+	if((nargv = malloc (sizeof (char *) * (argc + 4))) == NULL) {
+	    errx(1, "malloc failure");
+	}
+
+	nargv[argc + 3] = NULL;
+	for (i = argc; i >= optind; i--)
+	    nargv[i + 3] = argv[i];
+	np = &nargv[i + 3];
+
 	argv += optind;
 
 	errno = 0;
@@ -153,7 +168,6 @@ main(argc, argv)
 		}
 
 	/* get target login information, default to root */
-	user = *argv ? *argv : "root";
 	if ((pwd = getpwnam(user)) == NULL) {
 		errx(1, "unknown login: %s", user);
 	}