pexec

commit d4ce7f18b993640e671c31892122426ce685835f
parent 9499528b65fa47723e8392cf8c320ff6cdd96723
Author: sin <sin@2f30.org>
Date:   Fri, 23 Mar 2018 11:52:58 +0000

Add -i to clear environment before exec

Diffstat:
M
Makefile
 | 
4
+++-
A
arg.h
 | 
50
++++++++++++++++++++++++++++++++++++++++++++++++++
M
pexec.c
 | 
27
+++++++++++++++------------

3 files changed, 68 insertions(+), 13 deletions(-)
diff --git a/Makefile b/Makefile
@@ -3,10 +3,12 @@ PREFIX = /usr/local
 SRC = pexec.c
 OBJ = pexec.o
 BIN = pexec
-DISTFILES = $(SRC) Makefile
+DISTFILES = $(SRC) Makefile arg.h
 
 all: $(BIN)
 
+pexec.o: arg.h
+
 clean:
 	rm -f $(OBJ) $(BIN) $(BIN)-$(VERSION).tar.gz
 
diff --git a/arg.h b/arg.h
@@ -0,0 +1,50 @@
+/*
+ * Copy me if you can.
+ * by 20h
+ */
+
+#ifndef ARG_H__
+#define ARG_H__
+
+extern char *argv0;
+
+/* use main(int argc, char *argv[]) */
+#define ARGBEGIN	for (argv0 = *argv, argv++, argc--;\
+					argv[0] && argv[0][0] == '-'\
+					&& argv[0][1];\
+					argc--, argv++) {\
+				char argc_;\
+				char **argv_;\
+				int brk_;\
+				if (argv[0][1] == '-' && argv[0][2] == '\0') {\
+					argv++;\
+					argc--;\
+					break;\
+				}\
+				int i_;\
+				for (i_ = 1, brk_ = 0, argv_ = argv;\
+						argv[0][i_] && !brk_;\
+						i_++) {\
+					if (argv_ != argv)\
+						break;\
+					argc_ = argv[0][i_];\
+					switch (argc_)
+
+#define ARGEND			}\
+			}
+
+#define ARGC()		argc_
+
+#define EARGF(x)	((argv[0][i_+1] == '\0' && argv[1] == NULL)?\
+				((x), abort(), (char *)0) :\
+				(brk_ = 1, (argv[0][i_+1] != '\0')?\
+					(&argv[0][i_+1]) :\
+					(argc--, argv++, argv[0])))
+
+#define ARGF()		((argv[0][i_+1] == '\0' && argv[1] == NULL)?\
+				(char *)0 :\
+				(brk_ = 1, (argv[0][i_+1] != '\0')?\
+					(&argv[0][i_+1]) :\
+					(argc--, argv++, argv[0])))
+
+#endif
diff --git a/pexec.c b/pexec.c
@@ -27,6 +27,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include "arg.h"
+
+char *argv0;
 
 static int
 memfd_create(const char *name, unsigned int flags)
@@ -75,27 +78,27 @@ xwrite(int fd, const void *buf, size_t nbytes)
 }
 
 static void
-pexec(int fd, int argc, char *argv[], char *envp[])
-{
-	if (fexecve(fd, argv, envp) < 0)
-		err(1, "fexecve");
-}
-
-static void
 usage(void)
 {
-	fprintf(stderr, "usage: pexec argv[0] [argv[1]...]\n");
+	fprintf(stderr, "usage: pexec [-i] argv[0] [argv[1]...]\n");
 	exit(1);
 }
 
 int
 main(int argc, char *argv[])
 {
+	char *envp[] = { NULL };
 	char buf[BUFSIZ];
 	ssize_t n;
-	int fd;
+	int fd, iflag = 0;
 
-	if (argc < 2)
+	ARGBEGIN {
+	case 'i':
+		iflag = 1;
+		break;
+	} ARGEND
+
+	if (argc == 0)
 		usage();
 
 	fd = memfd_create("exec", 0);
@@ -105,8 +108,8 @@ main(int argc, char *argv[])
 	while ((n = xread(STDIN_FILENO, buf, BUFSIZ)) > 0)
 		xwrite(fd, buf, n);
 
-	argc--, argv++;
 	extern char **environ;
-	pexec(fd, argc, argv, environ);
+	if (fexecve(fd, argv, iflag ? envp : environ) < 0)
+		err(1, "fexecve");
 	/* unreachable */
 }