Hello!
I try to write a small simple ssh client program to learn how to work with
libssh2.
I have the next code:
...
/* Request a shell */
channel = libssh2_channel_open_session(session);
if (!channel) {
fprintf(stderr, "Unable to open a session\n");
return (EXIT_FAILURE);
}
/* Request a terminal with 'vanilla' terminal emulation */
rc = libssh2_channel_request_pty(channel, "vanilla");
if (rc) {
fprintf(stderr, "Failed requesting pty\n");
return (EXIT_FAILURE);
}
/* Open a SHELL on that pty */
rc = libssh2_channel_shell(channel);
if (rc) {
fprintf(stderr, "Unable to request shell on allocated pty\n");
return (EXIT_FAILURE);
}
/* Main loop starts here.
* In it you will be requested to input a command
* command will be executed at remote side
* an you will get output from it */
do {
/* Request for command input */
printf("$ ");
fgets(command, BUFSIZ, stdin);
printf("Command is %s", command);
if (strcmp(command, "\n") == 0) {
printf("Empty command\n");
continue;
}
/* Write command to stdin of remote shell */
rc = libssh2_channel_write(channel, command, strlen(command));
printf("Channel write return value is %d\n", rc);
/* Read output from remote side */
rc = libssh2_channel_read(channel, inputbuf, BUFSIZ);
printf("Channel write return value is %d\n", rc);
printf("Remote side output:\n %s\n", inputbuf);
} while (strcmp(command, EXIT_COMMAND) != 0);
/* Main loop ends here */
...
The problem is that I get the output of the current command only when
executing the next one. How should I know that execution of the current
command is finished on remote side and I can use lbssh2_channel_read to
read it?
The whole program it attachment.
Thank you
BR
Ivan Tretyakov
/*
============================================================================
Name : SmallSimpleSSH.c
Author : Ivan Tretyakov
Version : 0.1
Copyright : GPLv3
Description : Libssh2 usage example
============================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <libssh2.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define EXIT_COMMAND "exit\n"
/* Main function */
int main(void) {
/* Configurable variables */
const char *username = "root";
const char *password = "root";
const char *hostaddr = "192.168.0.13";
/* Variables to don't touch */
int rc;
int sock;
struct sockaddr_in sin;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
char command[BUFSIZ];
char inputbuf[BUFSIZ];
/* Libss2 init block */
rc = libssh2_init(0);
if (rc) {
fprintf(stderr, "Error: libssh_init()\n");
return (EXIT_FAILURE);
}
/* Creating socket */
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock == -1) {
perror("socket");
return (EXIT_FAILURE);
}
/* Connect this socket to remote side */
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
sin.sin_addr.s_addr = inet_addr(hostaddr);
if (connect(sock, (struct sockaddr*)(&sin),
sizeof(struct sockaddr_in)) != 0) {
fprintf(stderr, "Failed to connect\n");
return (EXIT_FAILURE);
}
/* Create a session instance and start it up. This will trade welcome
* banners, exchange keys, and setup crypto, compression, and MAC layers */
session = libssh2_session_init();
if (!session) {
fprintf(stderr, "SSH init failed\n");
return (EXIT_FAILURE);
}
/* Handshake for session */
rc = libssh2_session_handshake(session, sock);
if (rc) {
fprintf(stderr, "SSH handshake failed\n");
return (EXIT_FAILURE);
}
/* Lets authenticate */
rc = libssh2_userauth_password(session, username, password);
if (rc) {
printf("Authentication by password failed\n");
return (EXIT_FAILURE);
} else {
printf("Authentication by password succeeded\n");
}
/* Request a shell */
channel = libssh2_channel_open_session(session);
if (!channel) {
fprintf(stderr, "Unable to open a session\n");
return (EXIT_FAILURE);
}
/* Request a terminal with 'vanilla' terminal emulation */
rc = libssh2_channel_request_pty(channel, "vanilla");
if (rc) {
fprintf(stderr, "Failed requesting pty\n");
return (EXIT_FAILURE);
}
/* Open a SHELL on that pty */
rc = libssh2_channel_shell(channel);
if (rc) {
fprintf(stderr, "Unable to request shell on allocated pty\n");
return (EXIT_FAILURE);
}
/* Main loop starts here.
* In it you will be requested to input a command
* command will be executed at remote side
* an you will get output from it */
do {
/* Request for command input */
printf("$ ");
fgets(command, BUFSIZ, stdin);
printf("Command is %s", command);
if (strcmp(command, "\n") == 0) {
printf("Empty command\n");
continue;
}
/* Write command to stdin of remote shell */
rc = libssh2_channel_write(channel, command, strlen(command));
printf("Channel write return value is %d\n", rc);
/* Read output from remote side */
rc = libssh2_channel_read(channel, inputbuf, BUFSIZ);
printf("Channel write return value is %d\n", rc);
printf("Remote side output:\n %s\n", inputbuf);
} while (strcmp(command, EXIT_COMMAND) != 0);
/* Main loop ends here */
/* De-init and pre-exit actions */
if (channel) {
libssh2_channel_free(channel);
channel = NULL;
}
rc = libssh2_session_disconnect(session, "Normal Shutdown");
if (rc) {
fprintf(stderr, "Session disconnect error\n");
return (EXIT_FAILURE);
} else
printf("Session finished successful\n");
libssh2_session_free(session);
close(sock);
libssh2_exit();
return (EXIT_SUCCESS);
}
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