Add warn() and die()

Given slstatus is a tool that runs in the background, most likely run
from .xinitrc, it's important to prepend the name of the tool to error
messages so it becomes clear where the error is coming from.

To make this much more consistent, this commit adds warn() and die()
utility functions consistent with other suckless projects and adapts all
calls to fprintf(stderr, *) to the warn() and die() functions, greatly
increasing the readability of the code.

components/battery.c

@@ -59,13 +59,12 @@
 
 		fd = open("/dev/apm", O_RDONLY);
 		if (fd < 0) {
-			fprintf(stderr, "open '/dev/apm': %s\n", strerror(errno));
+			warn("open '/dev/apm':");
 			return NULL;
 		}
 
 		if (ioctl(fd, APM_IOC_GETPOWER, &apm_info) < 0) {
-			fprintf(stderr, "ioctl 'APM_IOC_GETPOWER': %s\n",
-			        strerror(errno));
+			warn("ioctl 'APM_IOC_GETPOWER':");
 			close(fd);
 			return NULL;
 		}
@@ -90,13 +89,12 @@
 
 		fd = open("/dev/apm", O_RDONLY);
 		if (fd < 0) {
-			fprintf(stderr, "open '/dev/apm': %s\n", strerror(errno));
+			warn("open '/dev/apm':");
 			return NULL;
 		}
 
 		if (ioctl(fd, APM_IOC_GETPOWER, &apm_info) < 0) {
-			fprintf(stderr, "ioctl 'APM_IOC_GETPOWER': %s\n",
-			        strerror(errno));
+			warn("ioctl 'APM_IOC_GETPOWER':");
 			close(fd);
 			return NULL;
 		}

components/cpu.c

@@ -57,7 +57,7 @@
 		size = sizeof(freq);
 
 		if (sysctl(mib, 2, &freq, &size, NULL, 0) < 0) {
-			fprintf(stderr, "sysctl 'HW_CPUSPEED': %s\n", strerror(errno));
+			warn("sysctl 'HW_CPUSPEED':");
 			return NULL;
 		}
 
@@ -80,7 +80,7 @@
 
 		memcpy(b, a, sizeof(b));
 		if (sysctl(mib, 2, &a, &size, NULL, 0) < 0) {
-			fprintf(stderr, "sysctl 'KERN_CPTIME': %s\n", strerror(errno));
+			warn("sysctl 'KERN_CPTIME':");
 			return NULL;
 		}
 		if (!valid) {

components/datetime.c

@@ -11,7 +11,7 @@ datetime(const char *fmt)
 
 	t = time(NULL);
 	if (!strftime(buf, sizeof(buf), fmt, localtime(&t))) {
-		fprintf(stderr, "strftime: Result string exceeds buffer size\n");
+		warn("strftime: Result string exceeds buffer size");
 		return NULL;
 	}
 

components/disk.c

@@ -12,7 +12,7 @@ disk_free(const char *mnt)
 	struct statvfs fs;
 
 	if (statvfs(mnt, &fs) < 0) {
-		fprintf(stderr, "statvfs '%s': %s\n", mnt, strerror(errno));
+		warn("statvfs '%s':", mnt);
 		return NULL;
 	}
 
@@ -26,7 +26,7 @@ disk_perc(const char *mnt)
 	struct statvfs fs;
 
 	if (statvfs(mnt, &fs) < 0) {
-		fprintf(stderr, "statvfs '%s': %s\n", mnt, strerror(errno));
+		warn("statvfs '%s':", mnt);
 		return NULL;
 	}
 
@@ -40,7 +40,7 @@ disk_total(const char *mnt)
 	struct statvfs fs;
 
 	if (statvfs(mnt, &fs) < 0) {
-		fprintf(stderr, "statvfs '%s': %s\n", mnt, strerror(errno));
+		warn("statvfs '%s':", mnt);
 		return NULL;
 	}
 
@@ -54,7 +54,7 @@ disk_used(const char *mnt)
 	struct statvfs fs;
 
 	if (statvfs(mnt, &fs) < 0) {
-		fprintf(stderr, "statvfs '%s': %s\n", mnt, strerror(errno));
+		warn("statvfs '%s':", mnt);
 		return NULL;
 	}
 

components/hostname.c

@@ -10,7 +10,7 @@ const char *
 hostname(void)
 {
 	if (gethostname(buf, sizeof(buf)) < 0) {
-		fprintf(stderr, "gethostbyname: %s\n", strerror(errno));
+		warn("gethostbyname:");
 		return NULL;
 	}
 

components/ip.c

@@ -19,7 +19,7 @@ ipv4(const char *iface)
 	char host[NI_MAXHOST];
 
 	if (getifaddrs(&ifaddr) < 0) {
-		fprintf(stderr, "getifaddrs: %s\n", strerror(errno));
+		warn("getifaddrs:");
 		return NULL;
 	}
 
@@ -32,7 +32,7 @@ ipv4(const char *iface)
 		if (!strcmp(ifa->ifa_name, iface) &&
 		    (ifa->ifa_addr->sa_family == AF_INET)) {
 			if (s != 0) {
-				fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s));
+				warn("getnameinfo: %s", gai_strerror(s));
 				return NULL;
 			}
 			return bprintf("%s", host);
@@ -52,7 +52,7 @@ ipv6(const char *iface)
 	char host[NI_MAXHOST];
 
 	if (getifaddrs(&ifaddr) < 0) {
-		fprintf(stderr, "getifaddrs: %s\n", strerror(errno));
+		warn("getifaddrs:");
 		return NULL;
 	}
 
@@ -65,7 +65,7 @@ ipv6(const char *iface)
 		if (!strcmp(ifa->ifa_name, iface) &&
 		    (ifa->ifa_addr->sa_family == AF_INET6)) {
 			if (s != 0) {
-				fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s));
+				warn("getnameinfo: %s", gai_strerror(s));
 				return NULL;
 			}
 			return bprintf("%s", host);

components/kernel_release.c

@@ -12,7 +12,7 @@ kernel_release(void)
 	struct utsname udata;
 
 	if (uname(&udata) < 0) {
-		fprintf(stderr, "uname: %s\n", strerror(errno));
+		warn("uname:");
 		return NULL;
 	}
 

components/keyboard_indicators.c

@@ -11,7 +11,7 @@ keyboard_indicators(void)
 	XKeyboardState state;
 
 	if (!(dpy = XOpenDisplay(NULL))) {
-		fprintf(stderr, "Cannot open display\n");
+		warn("XOpenDisplay: Failed to open display");
 		return NULL;
 	}
 	XGetKeyboardControl(dpy, &state);

components/load_avg.c

@@ -10,7 +10,7 @@ load_avg(const char *fmt)
 	double avgs[3];
 
 	if (getloadavg(avgs, 3) < 0) {
-		fprintf(stderr, "getloadavg: Could not obtain load average.\n");
+		warn("getloadavg: Failed to obtain load average");
 		return NULL;
 	}
 

components/num_files.c

@@ -14,7 +14,7 @@ num_files(const char *dir)
 	int num;
 
 	if (!(fd = opendir(dir))) {
-		fprintf(stderr, "opendir '%s': %s\n", dir, strerror(errno));
+		warn("opendir '%s':", dir);
 		return NULL;
 	}
 

components/run_command.c

@@ -12,7 +12,7 @@ run_command(const char *cmd)
 	FILE *fp;
 
 	if (!(fp = popen(cmd, "r"))) {
-		fprintf(stderr, "popen '%s': %s\n", cmd, strerror(errno));
+		warn("popen '%s':", cmd);
 		return NULL;
 	}
 	p = fgets(buf, sizeof(buf) - 1, fp);

components/swap.c

@@ -13,11 +13,11 @@
 		size_t bytes_read;
 
 		if (!(fp = fopen(path, "r"))) {
-			fprintf(stderr, "fopen '%s': %s\n", path, strerror(errno));
+			warn("fopen '%s':", path);
 			return 0;
 		}
 		if (!(bytes_read = fread(buf, sizeof(char), bufsiz, fp))) {
-			fprintf(stderr, "fread '%s': %s\n", path, strerror(errno));
+			warn("fread '%s':", path);
 			fclose(fp);
 			return 0;
 		}
@@ -139,21 +139,21 @@
 
 		nswap = swapctl(SWAP_NSWAP, 0, 0);
 		if (nswap < 1) {
-			fprintf(stderr, "swaptctl 'SWAP_NSWAP': %s\n", strerror(errno));
+			warn("swaptctl 'SWAP_NSWAP':");
 		}
 
 		fsep = sep = calloc(nswap, sizeof(*sep));
 		if (!sep) {
-			fprintf(stderr, "calloc 'nswap': %s\n", strerror(errno));
+			warn("calloc 'nswap':");
 		}
 
 		rnswap = swapctl(SWAP_STATS, (void *)sep, nswap);
 		if (rnswap < 0) {
-			fprintf(stderr, "swapctl 'SWAP_STATA': %s\n", strerror(errno));
+			warn("swapctl 'SWAP_STATA':");
 		}
 
 		if (nswap != rnswap) {
-			fprintf(stderr, "SWAP_STATS != SWAP_NSWAP\n");
+			warn("getstats: SWAP_STATS != SWAP_NSWAP");
 		}
 
 		*total = 0;

components/temperature.c

@@ -36,8 +36,7 @@
 		size = sizeof(temp);
 
 		if (sysctl(mib, 5, &temp, &size, NULL, 0) < 0) {
-			fprintf(stderr, "sysctl 'SENSOR_TEMP': %s\n",
-			        strerror(errno));
+			warn("sysctl 'SENSOR_TEMP':");
 			return NULL;
 		}
 

components/uptime.c

@@ -50,7 +50,7 @@ format(int uptime)
 		size = sizeof(boottime);
 
 		if (sysctl(mib, 2, &boottime, &size, NULL, 0) < 0) {
-			fprintf(stderr, "sysctl 'KERN_BOOTTIME': %s\n", strerror(errno));
+			warn("sysctl 'KERN_BOOTTIME':");
 			return NULL;
 		}
 

components/user.c

@@ -20,7 +20,7 @@ username(void)
 	struct passwd *pw;
 
 	if (!(pw = getpwuid(geteuid()))) {
-		fprintf(stderr, "getpwuid '%d': %s\n", geteuid(), strerror(errno));
+		warn("getpwuid '%d':", geteuid());
 		return NULL;
 	}
 

components/volume.c

@@ -21,21 +21,19 @@ vol_perc(const char *card)
 	char *vnames[] = SOUND_DEVICE_NAMES;
 
 	if ((afd = open(card, O_RDONLY | O_NONBLOCK)) < 0) {
-		fprintf(stderr, "open '%s': %s\n", card, strerror(errno));
+		warn("open '%s':", card);
 		return NULL;
 	}
 
 	if (ioctl(afd, (int)SOUND_MIXER_READ_DEVMASK, &devmask) < 0) {
-		fprintf(stderr, "ioctl 'SOUND_MIXER_READ_DEVMASK': %s\n",
-		        strerror(errno));
+		warn("ioctl 'SOUND_MIXER_READ_DEVMASK':");
 		close(afd);
 		return NULL;
 	}
 	for (i = 0; i < LEN(vnames); i++) {
 		if (devmask & (1 << i) && !strcmp("vol", vnames[i])) {
 			if (ioctl(afd, MIXER_READ(i), &v) < 0) {
-				fprintf(stderr, "ioctl 'MIXER_READ(%ld)': %s\n", i,
-				        strerror(errno));
+				warn("ioctl 'MIXER_READ(%ld)':", i);
 				close(afd);
 				return NULL;
 			}

components/wifi.c

@@ -26,8 +26,7 @@
 		snprintf(path, sizeof(path), "%s%s%s", "/sys/class/net/", iface,
 		         "/operstate");
 		if (!(fp = fopen(path, "r"))) {
-			fprintf(stderr, "fopen '%s': %s\n", path,
-			        strerror(errno));
+			warn("fopen '%s':", path);
 			return NULL;
 		}
 		p = fgets(status, 5, fp);
@@ -37,8 +36,7 @@
 		}
 
 		if (!(fp = fopen("/proc/net/wireless", "r"))) {
-			fprintf(stderr, "fopen '/proc/net/wireless': %s\n",
-			        strerror(errno));
+			warn("fopen '/proc/net/wireless':");
 			return NULL;
 		}
 
@@ -74,13 +72,12 @@
 		snprintf(wreq.ifr_name, sizeof(wreq.ifr_name), "%s", iface);
 
 		if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
-			fprintf(stderr, "socket 'AF_INET': %s\n",
-			        strerror(errno));
+			warn("socket 'AF_INET':");
 			return NULL;
 		}
 		wreq.u.essid.pointer = id;
 		if (ioctl(sockfd,SIOCGIWESSID, &wreq) < 0) {
-			fprintf(stderr, "ioctl 'SIOCGIWESSID': %s\n", strerror(errno));
+			warn("ioctl 'SIOCGIWESSID':");
 			close(sockfd);
 			return NULL;
 		}
@@ -111,22 +108,19 @@
 		memset(&bssid, 0, sizeof(bssid));
 		memset(nr, 0, sizeof(struct ieee80211_nodereq));
 		if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
-			fprintf(stderr, "socket 'AF_INET': %s\n",
-				strerror(errno));
+			warn("socket 'AF_INET':");
 			return 0;
 		}
 		strlcpy(bssid.i_name, iface, sizeof(bssid.i_name));
 		if ((ioctl(sockfd, SIOCG80211BSSID, &bssid)) < 0) {
-			fprintf(stderr, "ioctl 'SIOCG80211BSSID': %s\n",
-				strerror(errno));
+			warn("ioctl 'SIOCG80211BSSID':");
 			close(sockfd);
 			return 0;
 		}
 		strlcpy(nr->nr_ifname, iface, sizeof(nr->nr_ifname));
 		memcpy(&nr->nr_macaddr, bssid.i_bssid, sizeof(nr->nr_macaddr));
 		if ((ioctl(sockfd, SIOCG80211NODE, nr)) < 0 && nr->nr_rssi) {
-			fprintf(stderr, "ioctl 'SIOCG80211NODE': %s\n",
-				strerror(errno));
+			warn("ioctl 'SIOCG80211NODE':");
 			close(sockfd);
 			return 0;
 		}

slstatus.c

@@ -17,7 +17,6 @@ struct arg {
 	const char *args;
 };
 
-char *argv0;
 char buf[1024];
 static int done;
 static Display *dpy;
@@ -43,8 +42,7 @@ difftimespec(struct timespec *res, struct timespec *a, struct timespec *b)
 static void
 usage(void)
 {
-	fprintf(stderr, "usage: %s [-s]\n", argv0);
-	exit(1);
+	die("usage: %s [-s]", argv0);
 }
 
 int
@@ -80,14 +78,12 @@ main(int argc, char *argv[])
 	}
 
 	if (!sflag && !(dpy = XOpenDisplay(NULL))) {
-		fprintf(stderr, "XOpenDisplay: Failed to open display\n");
-		return 1;
+		die("XOpenDisplay: Failed to open display");
 	}
 
 	while (!done) {
 		if (clock_gettime(CLOCK_MONOTONIC, &start) < 0) {
-			fprintf(stderr, "clock_gettime: %s\n", strerror(errno));
-			return 1;
+			die("clock_gettime:");
 		}
 
 		status[0] = '\0';
@@ -97,11 +93,10 @@ main(int argc, char *argv[])
 			}
 			if ((ret = snprintf(status + len, sizeof(status) - len,
 			                    args[i].fmt, res)) < 0) {
-				fprintf(stderr, "snprintf: %s\n",
-				        strerror(errno));
+				warn("snprintf:");
 				break;
 			} else if ((size_t)ret >= sizeof(status) - len) {
-				fprintf(stderr, "snprintf: Output truncated\n");
+				warn("snprintf: Output truncated");
 				break;
 			}
 			len += ret;
@@ -111,18 +106,14 @@ main(int argc, char *argv[])
 			printf("%s\n", status);
 		} else {
 			if (XStoreName(dpy, DefaultRootWindow(dpy), status) < 0) {
-				fprintf(stderr,
-				        "XStoreName: Allocation failed\n");
-				return 1;
+				die("XStoreName: Allocation failed");
 			}
 			XFlush(dpy);
 		}
 
 		if (!done) {
 			if (clock_gettime(CLOCK_MONOTONIC, &current) < 0) {
-				fprintf(stderr, "clock_gettime: %s\n",
-				        strerror(errno));
-				return 1;
+				die("clock_gettime:");
 			}
 			difftimespec(&diff, &current, &start);
 
@@ -133,9 +124,7 @@ main(int argc, char *argv[])
 			if (wait.tv_sec >= 0) {
 				if (nanosleep(&wait, NULL) < 0 &&
 				    errno != EINTR) {
-					fprintf(stderr, "nanosleep: %s\n",
-					        strerror(errno));
-					return 1;
+					die("nanosleep:");
 				}
 			}
 		}
@@ -144,9 +133,7 @@ main(int argc, char *argv[])
 	if (!sflag) {
 		XStoreName(dpy, DefaultRootWindow(dpy), NULL);
 		if (XCloseDisplay(dpy) < 0) {
-			fprintf(stderr,
-			        "XCloseDisplay: Failed to close display\n");
-			return 1;
+			die("XCloseDisplay: Failed to close display");
 		}
 	}
 

util.c

@@ -2,10 +2,52 @@
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "util.h"
 
+char *argv0;
+
+static void
+verr(const char *fmt, va_list ap)
+{
+	if (argv0 && strncmp(fmt, "usage", sizeof("usage") - 1)) {
+		fprintf(stderr, "%s: ", argv0);
+	}
+
+	vfprintf(stderr, fmt, ap);
+
+	if (fmt[0] && fmt[strlen(fmt) - 1] == ':') {
+		fputc(' ', stderr);
+		perror(NULL);
+	} else {
+		fputc('\n', stderr);
+	}
+}
+
+void
+warn(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	verr(fmt, ap);
+	va_end(ap);
+}
+
+void
+die(const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	verr(fmt, ap);
+	va_end(ap);
+
+	exit(1);
+}
+
 const char *
 bprintf(const char *fmt, ...)
 {
@@ -14,9 +56,9 @@ bprintf(const char *fmt, ...)
 
 	va_start(ap, fmt);
 	if ((ret = vsnprintf(buf, sizeof(buf), fmt, ap)) < 0) {
-		fprintf(stderr, "vsnprintf: %s\n", strerror(errno));
+		warn("vsnprintf:");
 	} else if ((size_t)ret >= sizeof(buf)) {
-		fprintf(stderr, "vsnprintf: Output truncated\n");
+		warn("vsnprintf: Output truncated");
 	}
 	va_end(ap);
 
@@ -31,7 +73,7 @@ pscanf(const char *path, const char *fmt, ...)
 	int n;
 
 	if (!(fp = fopen(path, "r"))) {
-		fprintf(stderr, "fopen '%s': %s\n", path, strerror(errno));
+		warn("fopen '%s':", path);
 		return -1;
 	}
 	va_start(ap, fmt);

util.h

@@ -3,5 +3,10 @@ extern char buf[1024];
 
 #define LEN(x) (sizeof (x) / sizeof *(x))
 
+extern char *argv0;
+
+void warn(const char *, ...);
+void die(const char *, ...);
+
 const char *bprintf(const char *fmt, ...);
 int pscanf(const char *path, const char *fmt, ...);