1
我正在研究一个C程序，它连接到数据库，抓取设备列表，然后分叉请求并创建到该设备的SSH连接。我遇到的问题是，具有700个结果的查询始终从碰到5个分支后开始。从本质上讲，我已经研究了pthread和glibc来处理线程，但是我发现的一些例子没有按需要工作，或者增加了太多的复杂性。C分叉5个孩子后停止
我遇到的问题是，它会停在5个孩子，并停止，而不是完成700个设备的其余部分。
示例代码：后connect_to_device回报
#include <libssh2.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/select.h>
#include <unistd.h>
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
#include <limits.h>
#include <mysql.h>
/********************************
*
* gcc -o confmgr cfgmgr.c -Wall -lpthread -lz -lm -lrt -ldl -lssh2 $(mysql_config --cflags) $(mysql_config --libs) -std=gnu99
*
********************************/
static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
{
struct timeval timeout;
int rc;
fd_set fd;
fd_set *writefd = NULL;
fd_set *readfd = NULL;
int dir;
timeout.tv_sec = 10;
timeout.tv_usec = 0;
FD_ZERO(&fd);
FD_SET(socket_fd, &fd);
/* now make sure we wait in the correct direction */
dir = libssh2_session_block_directions(session);
if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
readfd = &fd;
if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
writefd = &fd;
rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
return rc;
}
int *connect_to_device(MYSQL_RES** args){
printf("%s", args[2]);
const char *hostname = "1.1.1.1";
const char *commandline = "command_to_run ";
const char *username = "static_user";
const char *password = "static_pass";
unsigned long hostaddr;
int sock;
struct sockaddr_in sin;
const char *fingerprint;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
int rc;
int exitcode;
char *exitsignal=(char *)"none";
int bytecount = 0;
size_t len;
LIBSSH2_KNOWNHOSTS *nh;
int type;
rc = libssh2_init (0);
if (rc != 0) {
fprintf (stderr, "libssh2 initialization failed (%d)\n", rc);
return 1;
}
hostaddr = inet_addr(hostname);
/* Ultra basic "connect to port 22 on localhost"
* Your code is responsible for creating the socket establishing the
* connection
*/
sock = socket(AF_INET, SOCK_STREAM, 0);
sin.sin_family = AF_INET;
sin.sin_port = htons(22);
sin.sin_addr.s_addr = hostaddr;
if (connect(sock, (struct sockaddr*)(&sin),
sizeof(struct sockaddr_in)) != 0) {
fprintf(stderr, "failed to connect!\n");
return -1;
}
/* Create a session instance */
session = libssh2_session_init();
if (!session)
return -1;
/* tell libssh2 we want it all done non-blocking */
libssh2_session_set_blocking(session, 0);
/* ... start it up. This will trade welcome banners, exchange keys,
* and setup crypto, compression, and MAC layers
*/
while ((rc = libssh2_session_handshake(session, sock)) ==
LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Failure establishing SSH session: %d\n", rc);
return -1;
}
/* We could authenticate via password */
while ((rc = libssh2_userauth_password(session, username, password)) == LIBSSH2_ERROR_EAGAIN);
if (rc) {
fprintf(stderr, "Authentication by password failed.\n");
goto shutdown;
}
libssh2_trace(session, LIBSSH2_TRACE_TRANS | LIBSSH2_TRACE_KEX | LIBSSH2_TRACE_AUTH | LIBSSH2_TRACE_CONN | LIBSSH2_TRACE_SCP | LIBSSH2_TRACE_SFTP | LIBSSH2_TRACE_ERROR | LIBSSH2_TRACE_PUBLICKEY);
/* Exec non-blocking on the remove host */
while((channel = libssh2_channel_open_session(session)) == NULL &&
libssh2_session_last_error(session,NULL,NULL,0) == LIBSSH2_ERROR_EAGAIN)
{
waitsocket(sock, session);
}
if(channel == NULL)
{
fprintf(stderr,"Error\n");
exit(1);
}
while((rc = libssh2_channel_exec(channel, commandline)) == LIBSSH2_ERROR_EAGAIN)
{
waitsocket(sock, session);
}
if(rc != 0)
{
fprintf(stderr,"Error\n");
exit(1);
}
for(;;)
{
// loop until we block
int rc;
do
{
char buffer[0x4000];
/* strange thing */
sleep(1);
rc = libssh2_channel_read(channel, buffer, sizeof(buffer));
if(rc > 0)
{
int i;
for(i=0; i < rc; ++i)
putchar(buffer[i]);
}
}
while(rc > 0);
// this is due to blocking that would occur otherwise so we loop on this condition
if(rc == LIBSSH2_ERROR_EAGAIN)
{
waitsocket(sock, session);
}
else if(rc == 0)
break;
}
while((rc = libssh2_channel_close(channel)) == LIBSSH2_ERROR_EAGAIN)
;
if(rc == 0)
{
//does-not-work if(libssh2_channel_wait_closed(channel) == 0)
exitcode = libssh2_channel_get_exit_status(channel);
}
printf("\n%d\n", 221);
libssh2_channel_free(channel);
channel = NULL;
/***********************/
shutdown:
libssh2_session_disconnect(session, "Normal Shutdown, Thank you for playing");
libssh2_session_free(session);
close(sock);
fprintf(stderr, "\n----------------------\nScript Finished\n\n");
libssh2_exit();
return 7;
}
/********************************
*
*
*
*
********************************/
int main(int argc, char *argv[]){
pid_t childPID;
int children = 0;
MYSQL *conn;
MYSQL_RES *res;
MYSQL_ROW row;
char *mySQLserver = "localhost";
char *mySQLuser = "root";
char *mySQLpassword = ""; /* set me first */
char *mySQLdatabase = "Devices";
conn = mysql_init(NULL);
/* Connect to database */
if (!mysql_real_connect(conn, mySQLserver,
mySQLuser, mySQLpassword, mySQLdatabase, 0, NULL, 0)) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}
/* send SQL query */
if (mysql_query(conn, "SELECT Hostname,Descr,IP,Username,Password FROM All_Active_Devices")) {
fprintf(stderr, "%s\n", mysql_error(conn));
exit(1);
}
res = mysql_use_result(conn);
/* output table name */
printf("MySQL Tables in mysql database:\n");
while ((row = mysql_fetch_row(res)) != NULL){
printf("%s \n", row[0]);
children++; // Last fork() was successful
while (children >= 5)
{
int status;
// Wait for one child to exit
if (wait(&status) == 7)
{
children--;
}
}
childPID = fork();
if (childPID < 0) {
printf("Fork Error \n");
} else if (childPID == 0) {
printf("\tCreating Fork for %s: pid %d \n", row[0], childPID);
connect_to_device (&row);
}
else{
printf("\tDid not create Fork for %s \n", row[0]);
}
}
/* close connection */
mysql_free_result(res);
mysql_close(conn);
return 0;
}
谢谢，你说得对。他们正在用他们的PID而不是返回值退出。 –
谢谢，你是对的。像你的更新一样，'wait（）'返回PID。会做'if（wait（＆status）！= -1）{children--; '没问题，还是流程处理不好？ –
@sixeightzero这似乎是合理的，但如果你也获得'-1'，你应该可能会有某种错误处理。 –