simplify post-lock cmd and die if it fails

this patch does two things:

0. simplify the code by using posix_spawn()
1. unify the behavior of what happens if the post-lock cmd fails.

currently, if `fork()` fails, slock will die without locking the screen.
HOWEVER if `execvp()` fails it prints a message to stderr (which the
user cannot see since the screen has been locked already) and only exits
the child while the parent locks the screen.

to reproduce:

	# slock some_bin_that_doesnt_exist

this behavior is inconsistent, if the idea is that post-lock cmd is
_not_ important then we shouldn't `die()` on `fork()` failure either.
and if we assume that the post-lock cmd _is_ important, then we should
die on exec failure as well.

this patch assumes the latter and calls `die()` if `posix_spawn()`
fails.

LICENSE

@@ -4,6 +4,7 @@ MIT/X Consortium License
 © 2014 Dimitris Papastamos <sin@2f30.org>
 © 2006-2014 Anselm R Garbe <anselm@garbe.us>
 © 2014-2016 Laslo Hunhold <dev@frign.de>
+© 2016-2023 Hiltjo Posthuma <hiltjo@codemadness.org>
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),

Makefile

@@ -6,56 +6,41 @@ include config.mk
 SRC = slock.c ${COMPATSRC}
 OBJ = ${SRC:.c=.o}
 
-all: options slock
-
-options:
-	@echo slock build options:
-	@echo "CFLAGS   = ${CFLAGS}"
-	@echo "LDFLAGS  = ${LDFLAGS}"
-	@echo "CC       = ${CC}"
+all: slock
 
 .c.o:
-	@echo CC $<
-	@${CC} -c ${CFLAGS} $<
+	${CC} -c ${CFLAGS} $<
 
 ${OBJ}: config.h config.mk arg.h util.h
 
 config.h:
-	@echo creating $@ from config.def.h
-	@cp config.def.h $@
+	cp config.def.h $@
 
 slock: ${OBJ}
-	@echo CC -o $@
-	@${CC} -o $@ ${OBJ} ${LDFLAGS}
+	${CC} -o $@ ${OBJ} ${LDFLAGS}
 
 clean:
-	@echo cleaning
-	@rm -f slock ${OBJ} slock-${VERSION}.tar.gz
+	rm -f slock ${OBJ} slock-${VERSION}.tar.gz
 
 dist: clean
-	@echo creating dist tarball
-	@mkdir -p slock-${VERSION}
-	@cp -R LICENSE Makefile README slock.1 config.mk \
+	mkdir -p slock-${VERSION}
+	cp -R LICENSE Makefile README slock.1 config.mk \
 		${SRC} config.def.h arg.h util.h slock-${VERSION}
-	@tar -cf slock-${VERSION}.tar slock-${VERSION}
-	@gzip slock-${VERSION}.tar
-	@rm -rf slock-${VERSION}
+	tar -cf slock-${VERSION}.tar slock-${VERSION}
+	gzip slock-${VERSION}.tar
+	rm -rf slock-${VERSION}
 
 install: all
-	@echo installing executable file to ${DESTDIR}${PREFIX}/bin
-	@mkdir -p ${DESTDIR}${PREFIX}/bin
-	@cp -f slock ${DESTDIR}${PREFIX}/bin
-	@chmod 755 ${DESTDIR}${PREFIX}/bin/slock
-	@chmod u+s ${DESTDIR}${PREFIX}/bin/slock
-	@echo installing manual page to ${DESTDIR}${MANPREFIX}/man1
-	@mkdir -p ${DESTDIR}${MANPREFIX}/man1
-	@sed "s/VERSION/${VERSION}/g" <slock.1 >${DESTDIR}${MANPREFIX}/man1/slock.1
-	@chmod 644 ${DESTDIR}${MANPREFIX}/man1/slock.1
+	mkdir -p ${DESTDIR}${PREFIX}/bin
+	cp -f slock ${DESTDIR}${PREFIX}/bin
+	chmod 755 ${DESTDIR}${PREFIX}/bin/slock
+	chmod u+s ${DESTDIR}${PREFIX}/bin/slock
+	mkdir -p ${DESTDIR}${MANPREFIX}/man1
+	sed "s/VERSION/${VERSION}/g" <slock.1 >${DESTDIR}${MANPREFIX}/man1/slock.1
+	chmod 644 ${DESTDIR}${MANPREFIX}/man1/slock.1
 
 uninstall:
-	@echo removing executable file from ${DESTDIR}${PREFIX}/bin
-	@rm -f ${DESTDIR}${PREFIX}/bin/slock
-	@echo removing manual page from ${DESTDIR}${MANPREFIX}/man1
-	@rm -f ${DESTDIR}${MANPREFIX}/man1/slock.1
+	rm -f ${DESTDIR}${PREFIX}/bin/slock
+	rm -f ${DESTDIR}${MANPREFIX}/man1/slock.1
 
-.PHONY: all options clean dist install uninstall
+.PHONY: all clean dist install uninstall

config.mk

@@ -27,6 +27,3 @@ COMPATSRC = explicit_bzero.c
 #CPPFLAGS = -DVERSION=\"${VERSION}\" -D_BSD_SOURCE -D_NETBSD_SOURCE
 # On OpenBSD set COMPATSRC to empty
 #COMPATSRC =
-
-# compiler and linker
-CC = cc

slock.1

@@ -1,5 +1,6 @@
-.Dd 2016-08-23
+.Dd October 6, 2023
 .Dt SLOCK 1
+.Os
 .Sh NAME
 .Nm slock
 .Nd simple X screen locker
@@ -9,31 +10,36 @@
 .Op Ar cmd Op Ar arg ...
 .Sh DESCRIPTION
 .Nm
-is a simple X screen locker. If provided,
-.Ar cmd Op Ar arg ...
+is a simple X screen locker.
+If provided,
+.Ar cmd
 is executed after the screen has been locked.
-.Sh OPTIONS
+.Pp
+The options are as follows:
 .Bl -tag -width Ds
 .It Fl v
 Print version information to stdout and exit.
 .El
+.Sh EXIT STATUS
+.Ex -std
+.Sh EXAMPLES
+$
+.Nm
+/usr/sbin/s2ram
 .Sh SECURITY CONSIDERATIONS
 To make sure a locked screen can not be bypassed by switching VTs
 or killing the X server with Ctrl+Alt+Backspace, it is recommended
 to disable both in
 .Xr xorg.conf 5
 for maximum security:
-.Bd -literal -offset left
+.Bd -literal
 Section "ServerFlags"
 	Option "DontVTSwitch" "True"
 	Option "DontZap"      "True"
 EndSection
 .Ed
-.Sh EXAMPLES
-$
-.Nm
-/usr/sbin/s2ram
 .Sh CUSTOMIZATION
 .Nm
 can be customized by creating a custom config.h from config.def.h and
-(re)compiling the source code. This keeps it fast, secure and simple.
+(re)compiling the source code.
+This keeps it fast, secure and simple.

slock.c

@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include <spawn.h>
 #include <sys/types.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/keysym.h>
@@ -317,7 +318,7 @@ main(int argc, char **argv) {
 
 	ARGBEGIN {
 	case 'v':
-		fprintf(stderr, "slock-"VERSION"\n");
+		puts("slock-"VERSION);
 		return 0;
 	default:
 		usage();
@@ -376,15 +377,12 @@ main(int argc, char **argv) {
 
 	/* run post-lock command */
 	if (argc > 0) {
-		switch (fork()) {
-		case -1:
-			die("slock: fork failed: %s\n", strerror(errno));
-		case 0:
-			if (close(ConnectionNumber(dpy)) < 0)
-				die("slock: close: %s\n", strerror(errno));
-			execvp(argv[0], argv);
-			fprintf(stderr, "slock: execvp %s: %s\n", argv[0], strerror(errno));
-			_exit(1);
+		pid_t pid;
+		extern char **environ;
+		int err = posix_spawnp(&pid, argv[0], NULL, NULL, argv, environ);
+		if (err) {
+			die("slock: failed to execute post-lock command: %s: %s\n",
+			    argv[0], strerror(err));
 		}
 	}