Hi,

I need to fetch a file from remote system using scp through a C programme.(basically not to enter passwd manually)
As we need to capture the prasswd promting in the programme i using the pipe.

Here is the my sample progrmme.



bool getRemoteFile(char *ip,char *user,char *passwd,char *srcFile,char *dstFile,char *errBuf)
{

char *exe = "/usr/bin/scp";
int result=0,ret = 0, pid=0;
int write_stdin[2], read_stdout[2];
char response[512];
char inputString[1024];
char *argv[10] = {exe,inputString,dstFile,NULL};

snprintf(inputString, 1023, "%s@%s:%s", user,Ip, srcFile);

pipe(write_stdin);
pipe(read_stdout);

/* Fork the process */
pid = fork();

switch (pid) {
case 0: /* Child process */
close(write_stdin[1]);
close(read_stdout[0]);
/* Replace stdin and stdout with the new fds */
dup2(write_stdin[0], STDIN_FILENO);
dup2(read_stdout[1], STDERR_FILENO);
dup2(read_stdout[1], STDOUT_FILENO);
close(write_stdin[0]);
close(read_stdout[1]);
execvp(exe, argv);
_exit(0);
break;
case -1: /* fork() error */
Log("Fork() error for host:%s, cmd:scp, user:%s", Ip,user);
break;
default: /* Parent process */
/* Close unneeded fds */
close(write_stdin[0]);
close(read_stdout[1]);
struct pollfd waitfordata[1];
waitfordata[0].fd=read_stdout[0];
waitfordata[0].events=POLLIN;
sleep(1);
int status;
int waittime=1;
// result = talkToIDPDevice(waitfordata,read_stdout[0], write_stdin[1], idpdevice->password);
do {
int err = poll(waitfordata, 1, 60000);
if (err == -1){
strncpy(errBuf,"poll failed failed",strlen("poll failed failed"));
return false;
}else{
if(err == 0 && waittime > 5 ){

/* Connection Timed Out
killl the child process
*/
kill(pid,9);
strncpy(errBuf,"Connection Timed Out",strlen("Connection Timed Out"));
return false;
}else{
memset(response,0,512);
read(read_stdout[0],response,511); /* process the buffer*/
if(strstr(response,"(yes/no)") == 0 ){
write(write_stdin[1],"yes",3);
write(write_stdin[1],"\n",2);
continue;
}else if(strstr(response,"password:") == 0 ){
write(write_stdin[1],passwd,strlen(passwd));
write(write_stdin[1],"\n",2);
break;
}
}
}
waittime++;

}while(1);
/* *call wait pid */
close(write_stdin[1]);
close(read_stdout[0]);
}
}


Generally using above programme we can execute a command in child and capture the output that command in parent.
Similarly i tried using scp command so that passwd prompting will received in the parent , but passwd prompting is going to STDOUT.

Why scp output was not captured in the parent.

Please help me.

Regards,
Ravikumar

Why don't you use a library like http://nixbit.com/cat/system/networking/ssh-library/?
Or, why don't you setup the machines so no password is asked?

setting no passwd not serves my purpose.
May be SSH library will do my work.

Is not possible doing through fork + exec + pipe + dup system calls ?

Regards,
Ravikumar

I think when he said 'no passwd' he meant use 'authorised keys' instead. Still secure, but cmd line passwd not reqd.