Fixed short process names in top

Conky takes process names from /proc/<pid>/stat and it's limited to 16
chars in kernel. That obviously makes top_name_width option to work only
for decreasing name length. To obtain longer names we parse
/proc/<pid>/cmdline.

Not every process has cmdline, so we take both process names and choose
one we want to use. Like this:

- Get process name from /proc/<pid>/stat

- Get process cmdline from /proc/<pid>/cmdline

- Transform cmdline to a bit simpler form(i.e. "/usr/bin/python
 /usr/bin/terminator" to "python /usr/bin/terminator"), keeping
the arguments(might be changed easily)

- Choose the one that is longer and use it

src/linux.cc

@@ -2584,8 +2584,10 @@ static void calc_io_each(void)
 static void process_parse_stat(struct process *process)
 {
 	char line[BUFFER_LEN] = { 0 }, filename[BUFFER_LEN], procname[BUFFER_LEN];
+	char cmdline[BUFFER_LEN] = { 0 }, cmdline_filename[BUFFER_LEN], cmdline_procname[BUFFER_LEN];
+	char tmpstr[BUFFER_LEN] = { 0 };
 	char state[4];
-	int ps;
+	int ps, cmdline_ps;
 	unsigned long user_time = 0;
 	unsigned long kernel_time = 0;
 	int rc;
@@ -2596,6 +2598,7 @@ static void process_parse_stat(struct process *process)
 	struct stat process_stat;
 
 	snprintf(filename, sizeof(filename), PROCFS_TEMPLATE, process->pid);
+	snprintf(cmdline_filename, sizeof(cmdline_filename), PROCFS_CMDLINE_TEMPLATE, process->pid);
 
 	ps = open(filename, O_RDONLY);
 	if (ps < 0) {
@@ -2616,6 +2619,54 @@ static void process_parse_stat(struct process *process)
 		return;
 	}
 
+	/* Read /proc/<pid>/cmdline */
+	cmdline_ps = open(cmdline_filename, O_RDONLY);
+	if (cmdline_ps < 0) {
+		/* The process must have finished in the last few jiffies! */
+		return;
+	}
+
+	endl = read(cmdline_ps, cmdline, BUFFER_LEN - 1);
+	close(cmdline_ps);
+	if (endl < 0) {
+		return;
+	}
+
+	/* Some processes have null-separated arguments, let's fix it */
+	for(int i = 0; i < endl; i++)
+		if (cmdline[i] == 0)
+			cmdline[i] = ' ';
+
+	cmdline[endl] = 0;
+	/* We want to transform for example "/usr/bin/python program.py" to "python program.py"
+	 * 1. search for first space
+	 * 2. search for last / before first space
+	 * 3. copy string from it's position */
+
+	char * space_ptr = strchr(cmdline, ' ');
+	if (space_ptr == NULL)
+	{
+		strcpy(tmpstr, cmdline);
+	}
+	else
+	{
+		long int space_pos = space_ptr - cmdline;
+		strncpy(tmpstr, cmdline, space_pos);
+		tmpstr[space_pos] = 0;
+	}
+
+	char * slash_ptr = strrchr(tmpstr, '/');
+	if (slash_ptr == NULL )
+	{
+		strncpy(cmdline_procname, cmdline, BUFFER_LEN);
+	}
+	else
+	{
+		long int slash_pos = slash_ptr - tmpstr;
+		strncpy(cmdline_procname, cmdline + slash_pos + 1, BUFFER_LEN - slash_pos);
+		cmdline_procname[BUFFER_LEN - slash_pos] = 0;
+	}
+
 	/* Extract cpu times from data in /proc filesystem */
 	lparen = strchr(line, '(');
 	rparen = strrchr(line, ')');
@@ -2625,6 +2676,10 @@ static void process_parse_stat(struct process *process)
 	rc = MIN((unsigned)(rparen - lparen - 1), sizeof(procname) - 1);
 	strncpy(procname, lparen + 1, rc);
 	procname[rc] = '\0';
+
+	if (strlen(procname) < strlen(cmdline_procname))
+		strncpy(procname, cmdline_procname, strlen(cmdline_procname)+1);
+
 	rc = sscanf(rparen + 1, "%3s %*s %*s %*s %*s %*s %*s %*s %*s %*s %*s %lu "
 			"%lu %*s %*s %*s %d %*s %*s %*s %llu %llu", state, &process->user_time,
 			&process->kernel_time, &nice_val, &process->vsize, &process->rss);