Add a libc function execvP that takes the search path as an arguement.

Change execvp to be a wrapper around execvP. This is necessary for some
of the /rescue pieces. It may also be more generally applicable as well.

Submitted by:	Tim Kientzle <kientzle@acm.org>
Approved by:	Silence on arch@

include/unistd.h

@@ -335,6 +335,7 @@ int	 execlp(const char *, const char *, ...);
 int	 execv(const char *, char * const *);
 int	 execve(const char *, char * const *, char * const *);
 int	 execvp(const char *, char * const *);
+int	 execvP(const char *, const char *, char * const *);
 pid_t	 fork(void);
 long	 fpathconf(int, int);
 char	*getcwd(char *, size_t);

lib/libc/gen/exec.3

@@ -41,7 +41,8 @@
 .Nm execle ,
 .Nm exect ,
 .Nm execv ,
-.Nm execvp
+.Nm execvp ,
+.Nm execvP
 .Nd execute a file
 .Sh LIBRARY
 .Lb libc
@@ -60,6 +61,8 @@
 .Fn execv "const char *path" "char *const argv[]"
 .Ft int
 .Fn execvp "const char *file" "char *const argv[]"
+.Ft int
+.Fn execvP "const char *file" "const char *search_path" "char *const argv[]"
 .Sh DESCRIPTION
 The
 .Nm exec
@@ -99,8 +102,9 @@ pointer.
 The
 .Fn exect ,
 .Fn execv ,
+.Fn execvp ,
 and
-.Fn execvp
+.Fn execvP
 functions provide an array of pointers to null-terminated strings that
 represent the argument list available to the new program.
 The first argument, by convention, should point to the file name associated
@@ -134,14 +138,19 @@ in the current process.
 Some of these functions have special semantics.
 .Pp
 The functions
-.Fn execlp
+.Fn execlp ,
+.Fn execvp ,
 and
-.Fn execvp
+.Fn execvP
 will duplicate the actions of the shell in searching for an executable file
 if the specified file name does not contain a slash
 .Dq Li /
 character.
-The search path is the path specified in the environment by
+For
+.Fn execlp
+and
+.Fn execvp ,
+search path is the path specified in the environment by
 .Dq Ev PATH
 variable.
 If this variable isn't specified,
@@ -151,6 +160,9 @@ definition in
 .Aq paths.h ,
 which is set to
 .Dq Ev /usr/bin:/bin .
+For
+.Fn execvP ,
+the search path is specified as an argument to the function.
 In addition, certain errors are treated specially.
 .Pp
 If an error is ambiguous (for simplicity, we shall consider all
@@ -206,9 +218,10 @@ The shell.
 The
 .Fn execl ,
 .Fn execle ,
-.Fn execlp
-and
+.Fn execlp ,
 .Fn execvp
+and
+.Fn execvP
 functions
 may fail and set
 .Va errno
@@ -300,3 +313,7 @@ and
 functions
 conform to
 .St -p1003.1-88 .
+The
+.Fn execvP
+function first appeared in
+.Fx 5.2 .

lib/libc/gen/exec.c

@@ -142,15 +142,27 @@ execv(name, argv)
 }
 
 int
-execvp(name, argv)
+execvp(const char *name, char *const *argv)
+{
+	const char *path;
+
+	/* Get the path we're searching. */
+	if (!(path = getenv("PATH")))
+		path = _PATH_DEFPATH;
+	return(execvP(name,path,argv));
+}
+
+int
+execvP(name, path, argv)
 	const char *name;
+	const char *path;
 	char * const *argv;
 {
 	char **memp;
 	int cnt, lp, ln;
 	char *p;
 	int eacces, save_errno;
-	char *bp, *cur, *path, buf[MAXPATHLEN];
+	char *bp, *cur, buf[MAXPATHLEN];
 	struct stat sb;
 
 	eacces = 0;
@@ -158,7 +170,7 @@ execvp(name, argv)
 	/* If it's an absolute or relative path name, it's easy. */
 	if (index(name, '/')) {
 		bp = (char *)name;
-		cur = path = NULL;
+		cur = NULL;
 		goto retry;
 	}
 	bp = buf;
@@ -169,16 +181,12 @@ execvp(name, argv)
 		return (-1);
 	}
 
-	/* Get the path we're searching. */
-	if (!(path = getenv("PATH")))
-		path = _PATH_DEFPATH;
 	cur = alloca(strlen(path) + 1);
 	if (cur == NULL) {
 		errno = ENOMEM;
 		return (-1);
 	}
 	strcpy(cur, path);
-	path = cur;
 	while ( (p = strsep(&cur, ":")) ) {
 		/*
 		 * It's a SHELL path -- double, leading and trailing colons
@@ -197,7 +205,7 @@ execvp(name, argv)
 		 * the user may execute the wrong program.
 		 */
 		if (lp + ln + 2 > sizeof(buf)) {
-			(void)_write(STDERR_FILENO, "execvp: ", 8);
+			(void)_write(STDERR_FILENO, "execvP: ", 8);
 			(void)_write(STDERR_FILENO, p, lp);
 			(void)_write(STDERR_FILENO, ": path too long\n",
 			    16);