后台运行Linux程序，可以通过crontab设置，这种方法一般用来让一个程序定时运行，也可以通过./test &这样在程序末尾加上一个&使程序在后台运行。
编写代码，下面我将参考httpd写一个程序使其运行不占控制台。
#include "detach.h"
void detach(void)
{
int x;
int pgrp;
chdir("/");
if ((x = fork()) > 0)
exit(0); //exit parent, so we have the child
else if (x == -1) {
perror("fork");
fprintf(stderr, "unable to fork new process\n");
exit(1);
}
raise(SIGSTOP);
/* setsid - run a program in a new session*/
if ((pgrp = setsid()) == -1) {
perror("setsid");
fprintf(stderr, "setsid failed\n");
exit(1);
}
/* close out the standard file descriptors */
if (freopen("/dev/null", "r", stdin) == NULL) {
fprintf(stderr, "unable to replace stdin with /dev/null:\n");
/* continue anyhow -- note we can't close out descriptor 0 because we
* have nothing to replace it with, and if we didn't have a descriptor
* 0 the next file would be created with that value ... leading to
* havoc.
*/
}
if (freopen("/dev/null", "w", stdout) == NULL) {
fprintf(stderr, "unable to replace stdout with /dev/null: \n");
}
/* stderr is a tricky one, we really want it to be the error_log,
* but we haven't opened that yet. So leave it alone for now and it'll
* be reopened moments later.
*/
}