slstatus

commit 07edc3434494e230cdad90e1910c8619551eddca
parent 9383bca29156ecbdb32e16e9d33e77e82693a8eb
Author: Santtu Lakkala <inz@inz.fi>
Date:   Sat, 26 Feb 2022 11:51:57 +0200

Add pipe_command component

pipe_command runs a command and provides the latest line of output from
it.

Diffstat:
M
Makefile
 | 
1
+
A
components/pipe_command.c
 | 
126
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
slstatus.c
 | 
1
+
M
slstatus.h
 | 
3
+++

4 files changed, 131 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -19,6 +19,7 @@ COM =\
 	components/load_avg\
 	components/netspeeds\
 	components/num_files\
+	components/pipe_command\
 	components/ram\
 	components/run_command\
 	components/separator\
diff --git a/components/pipe_command.c b/components/pipe_command.c
@@ -0,0 +1,126 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include "../util.h"
+
+static struct {
+	int fd;
+	int len;
+	int bused;
+	int neednl;
+	char last[256];
+	char buffer[256];
+	const char *cmd;
+} *pipes = NULL;
+int npipes = 0;
+
+char *find_last_seg(char *buffer, size_t n, char sep, int *len)
+{
+	char *i;
+	char *pp = NULL;
+	char *p = buffer - 1;
+
+	for (i = buffer; n--; i++) {
+		if (*i == sep) {
+			pp = p;
+			p = i;
+		}
+	}
+
+	if (pp) {
+		*len = p - pp - 1;
+		return pp + 1;
+	}
+
+	*len = -1;
+	return NULL;
+}
+
+const char *
+pipe_command(const char *cmd)
+{
+	int i;
+
+	for (i = 0; i < npipes && pipes[i].cmd != cmd; i++);
+	if (i == npipes) {
+		int pfd[2];
+		pipes = realloc(pipes, sizeof(*pipes) * ++npipes);
+		if (pipe(pfd))
+			die("failed to open pipe");
+		watch(pfd[0]);
+
+		switch (fork()) {
+		case -1:
+			die("fork failed");
+			break;
+		case 0:
+			close(pfd[0]);
+			close(STDIN_FILENO);
+			close(STDOUT_FILENO);
+			dup2(pfd[1], STDOUT_FILENO);
+			close(pfd[1]);
+			open("/dev/null", O_WRONLY);
+			execlp("sh", "sh", "-c", cmd, NULL);
+			exit(1);
+			break;
+		default:
+			close(pfd[1]);
+			fcntl(pfd[0], F_SETFL, O_NONBLOCK);
+			pipes[i].fd = pfd[0];
+			pipes[i].bused = 0;
+			pipes[i].len = 0;
+			pipes[i].cmd = cmd;
+			pipes[i].neednl = 0;
+			break;
+		}
+		npipes++;
+	}
+
+	int fd = pipes[i].fd;
+	int r;
+	char *nnl;
+	int len;
+
+	r = read(fd, pipes[i].buffer + pipes[i].bused,
+		 sizeof(pipes[i].buffer) - pipes[i].bused);
+
+	if (r == 0)
+		die("pipe source died");
+	if (r < 0) {
+		if (errno == EWOULDBLOCK || errno == EAGAIN)
+			r = 0;
+		else
+			die("pipe error:");
+	}
+
+	nnl = find_last_seg(pipes[i].buffer, r, '\n', &len);
+
+	if (nnl) {
+		if (!pipes[i].neednl || nnl != pipes[i].buffer) {
+			memcpy(pipes[i].last, nnl, len);
+			pipes[i].len = len;
+		}
+		pipes[i].neednl = 0;
+		pipes[i].bused = r - (nnl + len + 1 - pipes[i].buffer);
+		memmove(pipes[i].buffer, nnl + len + 1, pipes[i].bused);
+	} else if (!pipes[i].neednl) {
+		pipes[i].bused += r;
+
+		if (pipes[i].bused == sizeof(pipes[i].buffer)) {
+			pipes[i].len = pipes[i].bused;
+			memcpy(pipes[i].last, pipes[i].buffer,
+			       pipes[i].bused);
+			pipes[i].bused = 0;
+			pipes[i].neednl = 1;
+		}
+	}
+
+	if (pipes[i].len == 0)
+		return NULL;
+	return bprintf("%.*s", pipes[i].len, pipes[i].last);
+}
diff --git a/slstatus.c b/slstatus.c
@@ -96,6 +96,7 @@ main(int argc, char *argv[])
 		die("XOpenDisplay: Failed to open display");
 	}
 
+
 	do {
 		if (clock_gettime(CLOCK_MONOTONIC, &start) < 0) {
 			die("clock_gettime:");
diff --git a/slstatus.h b/slstatus.h
@@ -57,6 +57,9 @@ const char *ram_used(void);
 /* run_command */
 const char *run_command(const char *cmd);
 
+/* pipe_command */
+const char *pipe_command(const char *cmd);
+
 /* separator */
 const char *separator(const char *separator);