r331: Add code to detect whether a device is connected

[nbd.git] / nbd-client.c

diff --git a/nbd-client.c b/nbd-client.c
index 51927b1..4e4777b 100644 (file)
--- a/nbd-client.c
+++ b/nbd-client.c
@@ -28,6 +28,7 @@
 #include <syslog.h>
 #include <stdlib.h>
 #include <sys/mount.h>
+#include <errno.h>
 
 #ifndef __GNUC__
 #error I need GCC to work
@@ -37,6 +38,27 @@
 #define MY_NAME "nbd_client"
 #include "cliserv.h"
 
+int check_conn(char* devname) {
+       char buf[256];
+       int fd;
+       int len;
+       if(!strncmp(devname, "/dev/", 5)) {
+               devname+=5;
+       }
+       snprintf(buf, 256, "/sys/block/%s/pid", devname);
+       if((fd=open(buf, O_RDONLY))<0) {
+               if(errno==ENOENT) {
+                       return 1;
+               } else {
+                       return 2;
+               }
+       }
+       len=read(fd, buf, 256);
+       buf[len-1]='\0';
+       printf("%s\n", buf);
+       return 0;
+}
+
 int opennet(char *name, int port, int sdp) {
        int sock;
        struct sockaddr_in xaddrin;
@@ -191,6 +213,7 @@ int main(int argc, char *argv[]) {
                fprintf(stderr, "nbd-client version %s\n", PACKAGE_VERSION);
                fprintf(stderr, "Usage: nbd-client [bs=blocksize] [timeout=sec] host port nbd_device [-swap] [-persist]\n");
                fprintf(stderr, "Or   : nbd-client -d nbd_device\n");
+               fprintf(stderr, "Or   : nbd-client -c nbd_device\n");
                fprintf(stderr, "Default value for blocksize is 1024 (recommended for ethernet)\n");
                fprintf(stderr, "Allowed values for blocksize are 512,1024,2048,4096\n"); /* will be checked in kernel :) */
                fprintf(stderr, "Note, that kernel 2.4.2 and older ones do not work correctly with\n");
@@ -221,6 +244,9 @@ int main(int argc, char *argv[]) {
                printf("done\n");
                return 0;
        }
+       if(strcmp(argv[0], "-c")==0) {
+               return check_conn(argv[1]);
+       }
        
        if (strncmp(argv[0], "bs=", 3)==0) {
                blocksize=atoi(argv[0]+3);