2级a做爰片免费网站,酷家乐线下培训班,网站手机验证码怎么做,宁波电器网站制作目录 1. 代码#xff08;1#xff09;启动进程execvp#xff08;2#xff09;替换的新进程new_proc 2. 验证#xff08;1#xff09;new_proc与execvp源文件同一目录#xff08;2#xff09;new_proc与execvp软链接同一目录 3. 总结4. errno.h 用execvp软链接启动进程1启动进程execvp2替换的新进程new_proc 2. 验证1new_proc与execvp源文件同一目录2new_proc与execvp软链接同一目录 3. 总结4. errno.h 用execvp软链接启动进程execvp中进行进程替换执行进程new_procnew_proc如果用./表示的当前相对路径执行那么new_proc应该放在execvp源文件的同一目录还是execvp的软链接所在目录 1. 代码
1启动进程execvp
#include stdio.h
#include stdlib.h
#include unistd.h
#include errno.h
#include string.hint main(void)
{int pid 0;pid fork();if (pid 0){printf([%s,%d] fork failed, ret%d\n, __FUNCTION__, __LINE__, pid);}else if (pid 0){char *const argv[] {./new_proc, NULL};if (-1 execvp(argv[0], argv)){printf([%s,%d] execvp failed!, error: %s (%d)\n, __FUNCTION__, __LINE__, strerror(errno), errno);exit(1);}}for (;;){printf(pid %d\n, pid);sleep(1);}return 0;
}2替换的新进程new_proc
#include stdio.h
#include stdlib.h
#include unistd.hint main(int argc, char **argv)
{for (;;){printf(new_proc\n);sleep(1);}return 0;
}2. 验证
1new_proc与execvp源文件同一目录
[exec]$ pwd
/test/exec
[exec]$ ls -l *
lrwxrwxrwx 1 test test 14 Aug 17 13:44 execvp - package/execvp
package:
total 24
-rwxrwxr-x 1 test test 8808 Aug 17 13:49 execvp
-rwxrwxr-x 1 test test 8496 Aug 17 11:27 new_proc[exec]$ ./execvp
pid 13487
[main,21] execvp failed!, error: No such file or directory (2)
pid 13487
pid 13487[~]$ ps x | grep execvp
13486 pts/4 S 0:00 ./execvp
13487 pts/4 Z 0:00 [execvp] defunct
[~]$ cat /proc/13486/environ
...
PWD/test/exec执行会报错“No such file or directory”查看/proc/pid/environ其中包含了进程环境变量的列表发现包含了软链接路径但是没有源文件路径。
2new_proc与execvp软链接同一目录
[exec]$ ls -l *
lrwxrwxrwx 1 test test 14 Aug 17 13:44 execvp - package/execvp
-rwxrwxr-x 1 test test 8496 Aug 17 11:27 new_proc
package:
total 12
-rwxrwxr-x 1 test test 8808 Aug 17 14:51 execvp[exec]$ ./execvp
pid 25910
new_proc
pid 25910
new_proc可进行进程替换运行。
3. 总结
用软链接启动进程时进程的环境变量列表会包含软链接的路径但是没有源文件所在路径可通过/proc/pid/environ查看。 所以进程替换需要考虑软链接路径而不是源文件路径。
4. errno.h
使用strerror(errno)转换错误码为字符串的时候需要加上头文件#include string.h不然好像没有输出。
#define EPERM 1 /* Operation not permitted */
#define ENOENT 2 /* No such file or directory */
#define ESRCH 3 /* No such process */
#define EINTR 4 /* Interrupted system call */
#define EIO 5 /* I/O error */
#define ENXIO 6 /* No such device or address */
#define E2BIG 7 /* Argument list too long */
#define ENOEXEC 8 /* Exec format error */
#define EBADF 9 /* Bad file number */
#define ECHILD 10 /* No child processes */
#define EAGAIN 11 /* Try again */
#define ENOMEM 12 /* Out of memory */
#define EACCES 13 /* Permission denied */
#define EFAULT 14 /* Bad address */
#define ENOTBLK 15 /* Block device required */
#define EBUSY 16 /* Device or resource busy */
#define EEXIST 17 /* File exists */
#define EXDEV 18 /* Cross-device link */
#define ENODEV 19 /* No such device */
#define ENOTDIR 20 /* Not a directory */
#define EISDIR 21 /* Is a directory */
#define EINVAL 22 /* Invalid argument */
#define ENFILE 23 /* File table overflow */
#define EMFILE 24 /* Too many open files */
#define ENOTTY 25 /* Not a typewriter */
#define ETXTBSY 26 /* Text file busy */
#define EFBIG 27 /* File too large */
#define ENOSPC 28 /* No space left on device */
#define ESPIPE 29 /* Illegal seek */
#define EROFS 30 /* Read-only file system */
