Show usage message on invalid command line argument

[tl-append] / tl-append.c

diff --git a/tl-append.c b/tl-append.c
index 0650721f3fc90c32ee5d43d7449901bbe188cd90..a3e9a4ecb75fa40306fdadd4862d42f11ea0c0fe 100644 (file)
--- a/tl-append.c
+++ b/tl-append.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/file.h>
 #include <time.h>
 #include <unistd.h>
 
@@ -21,19 +22,36 @@ const struct timespec ACKNOWLEDGE_DELAY = {0, 300000000};
 
 typedef struct {
   int interactive;
+  int fcntl_lock;
+  int flock_lock;
 } conf_t;
 
-conf_t parse_command_line(int argc, char *argv[]) {
-  conf_t conf = {0};
+void usage() {
+  die("usage: tl-append [-i] [--no-fnctl-lock] [--no-flock-lock]");
+}
 
-  if (argc == 2 && strcmp(argv[1], "-i") == 0 && isatty(2))
-    conf.interactive = 1;
+conf_t parse_command_line(int argc, char *argv[]) {
+  conf_t conf;
+  conf.interactive = 0;
+  conf.fcntl_lock = 1;
+  conf.flock_lock = 1;
+
+  for (int i = 1; i < argc; i++) {
+    if (strcmp(argv[i], "-i") == 0 && isatty(2))
+      conf.interactive = 1;
+    else if (strcmp(argv[i], "--no-fnctl-lock") == 0)
+      conf.fcntl_lock = 0;
+    else if (strcmp(argv[i], "--no-flock-lock") == 0)
+      conf.flock_lock = 0;
+    else
+      usage();
+  }
 
   return conf;
 }
 
-static void read_line(conf_t conf, char *buf) {
-  if (conf.interactive)
+static void read_line(conf_t *conf, char *buf) {
+  if (conf->interactive)
     if (fputs(PROMPT, stderr) == EOF)
       die("I/O error writing prompt");
   if (fgets(buf, BUF_SIZE, stdin) == NULL) {
@@ -58,7 +76,9 @@ static void write_line(const char *now, FILE *f, const char *line) {
     die("Error writing to output file");
 }
 
-static void take_lock(FILE *f) {
+static void take_fcntl_lock(conf_t *conf, FILE *f) {
+  if (!conf->fcntl_lock)
+    return;
   struct flock lock;
   lock.l_type = F_WRLCK;
   lock.l_whence = SEEK_SET;
@@ -70,16 +90,38 @@ static void take_lock(FILE *f) {
   if (fcntl(fd, F_SETLK, &lock) == 0)
     return;
   if (errno != EACCES && errno != EAGAIN)
-    die_err("Couldn't take lock");
+    die_err("Couldn't take fcntl lock");
   if (fputs(WAITING, stderr) == EOF)
     die("Error writing waiting message");
   if (fcntl(fd, F_SETLKW, &lock) == 0)
     return;
-  die_err("Couldn't take lock");
+  die_err("Couldn't take fcntl lock");
+}
+
+static void take_flock_lock(conf_t *conf, FILE *f) {
+  if (!conf->flock_lock)
+    return;
+  int fd = fileno(f);
+  if (fd == -1)
+    die_err("Couldn't get file descriptor for locking");
+  if (flock(fd, LOCK_EX | LOCK_NB) == 0)
+    return;
+  if (errno != EWOULDBLOCK)
+    die_err("Couldn't take flock lock");
+  if (fputs(WAITING, stderr) == EOF)
+    die("Error writing waiting message");
+  if (flock(fd, LOCK_EX) == 0)
+    return;
+  die_err("Couldn't take flock lock");
+}
+
+static void take_lock(conf_t *conf, FILE *f) {
+  take_fcntl_lock(conf, f);
+  take_flock_lock(conf, f);
 }
 
-static void write_acknowledgment(conf_t conf) {
-  if (conf.interactive) {
+static void write_acknowledgment(conf_t *conf) {
+  if (conf->interactive) {
     if (fputs(ACKNOWLEDGE, stderr) == EOF)
       die("Error writing acknowledgment");
     if (nanosleep(&ACKNOWLEDGE_DELAY, NULL) == -1 && errno != EINTR)
@@ -87,11 +129,11 @@ static void write_acknowledgment(conf_t conf) {
   }
 }
 
-static void lock_and_write_line(conf_t conf, const char *line) {
+static void lock_and_write_line(conf_t *conf, const char *line) {
   const char *now = encode_time(time(NULL));
   FILE *f = fopen(FILENAME, "a");
 
-  take_lock(f);
+  take_lock(conf, f);
   write_line(now, f, line);
 
   if (fclose(f) != 0)
@@ -103,8 +145,8 @@ static void lock_and_write_line(conf_t conf, const char *line) {
 int main(int argc, char *argv[]) {
   conf_t conf = parse_command_line(argc, argv);
   char buf[BUF_SIZE];
-  for (read_line(conf, buf); buf[0]; read_line(conf, buf)) {
-    lock_and_write_line(conf, buf);
+  for (read_line(&conf, buf); buf[0]; read_line(&conf, buf)) {
+    lock_and_write_line(&conf, buf);
   }
   return 0;
 }