nginx学习—设置进程title(setproctitle)

刚好看到nginx设置进程title的源码，因此做一些总结。 linux进程实际是以argv[0]处的值来作为进程的title的，因此若需要修改进程的title只需要修改argv[0]处的值即可。 简单的方法就是直接将想要设置的title复制给argv[0]即可，如下示：

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> extern char** environ; int main(int argc, char* argv[]) { char s_title[] = "xiejian title for simple way!"; size_t i_size = strlen(s_title); memcpy(argv[0], s_title, i_size); argv[0][i_size] = '\0'; while(1){ system("ps -ef|awk '$8 ~ /xiejian/ {print $0}'"); sleep(10); } }

运行结果为： 但是这种方式是以破坏性的方式，进程的进程title的修改。由于程序的参数存储空间的后面紧跟的就是环境变量的存储位置，在不考虑参数的破坏性的情况下。 命令行参数argv和环境变量信息environ是在一块连续的内存中表示的，并且environ紧跟在argv后面。如下图： 由上图可知过长的title也会损坏环境变量environ的值。因此在nginx中，是将环境变量进行移位存储处理的。下面是nginx处理进程设置title的思路。

/* * To change the process title in Linux and Solaris we have to set argv[1] * to NULL and to copy the title to the same place where the argv[0] points to. * However, argv[0] may be too small to hold a new title. Fortunately, Linux * and Solaris store argv[] and environ[] one after another. So we should * ensure that is the continuous memory and then we allocate the new memory * for environ[] and copy it. After this we could use the memory starting * from argv[0] for our process title. * * The Solaris's standard /bin/ps does not show the changed process title. * You have to use "/usr/ucb/ps -w" instead. Besides, the UCB ps does not * show a new title if its length less than the origin command line length. * To avoid it we append to a new title the origin command line in the * parenthesis. */

然后由于nginx中考虑多进程的情况，因此他会在初始化时就完成environ的迁移。下面是初始化函数

//指向环境变量，默认的 extern char **environ; //指向之前的用于存放参数及环境变量的空间的最后位置。 static char *ngx_os_argv_last; ngx_int_t ngx_init_setproctitle(ngx_log_t *log) { u_char *p; size_t size; ngx_uint_t i; size = 0; //计算环境变量所用的总的空间的大小，然后以申请足够的空间用于存放环境变量 for (i = 0; environ[i]; i++) { size += ngx_strlen(environ[i]) + 1; } //为环境就是分配空间 p = ngx_alloc(size, log); if (p == NULL) { return NGX_ERROR; } //下面开始计算前面用于存放环境变量的最后位置 ngx_os_argv_last = ngx_os_argv[0]; //首先计算参数的最后位置 for (i = 0; ngx_os_argv[i]; i++) { if (ngx_os_argv_last == ngx_os_argv[i]) { ngx_os_argv_last = ngx_os_argv[i] + ngx_strlen(ngx_os_argv[i]) + 1; } } //再计算环境变量占用的最后位置，并完成环境变量的拷贝 for (i = 0; environ[i]; i++) { if (ngx_os_argv_last == environ[i]) { size = ngx_strlen(environ[i]) + 1; ngx_os_argv_last = environ[i] + size; ngx_cpystrn(p, (u_char *) environ[i], size); environ[i] = (char *) p; p += size; } } ngx_os_argv_last--; return NGX_OK; }

然后是具体的设置title的函数:

void ngx_setproctitle(char *title) { u_char *p; #if (NGX_SOLARIS) ngx_int_t i; size_t size; #endif ngx_os_argv[1] = NULL; p = ngx_cpystrn((u_char *) ngx_os_argv[0], (u_char *) "nginx: ", ngx_os_argv_last - ngx_os_argv[0]); p = ngx_cpystrn(p, (u_char *) title, ngx_os_argv_last - (char *) p); #if (NGX_SOLARIS) size = 0; for (i = 0; i < ngx_argc; i++) { size += ngx_strlen(ngx_argv[i]) + 1; } if (size > (size_t) ((char *) p - ngx_os_argv[0])) { /* * ngx_setproctitle() is too rare operation so we use * the non-optimized copies */ p = ngx_cpystrn(p, (u_char *) " (", ngx_os_argv_last - (char *) p); for (i = 0; i < ngx_argc; i++) { p = ngx_cpystrn(p, (u_char *) ngx_argv[i], ngx_os_argv_last - (char *) p); p = ngx_cpystrn(p, (u_char *) " ", ngx_os_argv_last - (char *) p); } if (*(p - 1) == ' ') { *(p - 1) = ')'; } } #endif if (ngx_os_argv_last - (char *) p) { ngx_memset(p, NGX_SETPROCTITLE_PAD, ngx_os_argv_last - (char *) p); } ngx_log_debug1(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0, "setproctitle: \"%s\"", ngx_os_argv[0]); }

最后就是根据nginx的思想的一个简单修改title的示例：

#include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #define NGX_OK 0 #define NGX_ERROR -1 #define NGX_SETPROCTITLE_PAD '\0' typedef int ngx_int_t; typedef unsigned int ngx_uint_t; extern char **environ; static char *ngx_os_argv_last; int ngx_argc; char **ngx_os_argv; u_char * ngx_cpystrn(u_char *dst, u_char *src, size_t n) { if (n == 0) { return dst; } while (--n) { *dst = *src; if (*dst == '\0') { return dst; } dst++; src++; } *dst = '\0'; return dst; } ngx_int_t ngx_init_setproctitle() { u_char *p; size_t size; ngx_uint_t i; size = 0; for (i = 0; environ[i]; i++) { size += strlen(environ[i]) + 1; } p = malloc(size); if (p == NULL) { return NGX_ERROR; } ngx_os_argv_last = ngx_os_argv[0]; for (i = 0; ngx_os_argv[i]; i++) { if (ngx_os_argv_last == ngx_os_argv[i]) { ngx_os_argv_last = ngx_os_argv[i] + strlen(ngx_os_argv[i]) + 1; } } for (i = 0; environ[i]; i++) { if (ngx_os_argv_last == environ[i]) { size = strlen(environ[i]) + 1; ngx_os_argv_last = environ[i] + size; ngx_cpystrn(p, (u_char *) environ[i], size); environ[i] = (char *) p; p += size; } } ngx_os_argv_last--; return NGX_OK; } void ngx_setproctitle(char *title) { u_char *p; ngx_os_argv[1] = NULL; p = ngx_cpystrn((u_char *) ngx_os_argv[0], (u_char *) "nginx: ", ngx_os_argv_last - ngx_os_argv[0]); p = ngx_cpystrn(p, (u_char *) title, ngx_os_argv_last - (char *) p); if (ngx_os_argv_last - (char *) p) { memset(p, NGX_SETPROCTITLE_PAD, ngx_os_argv_last - (char *) p); } } static ngx_int_t ngx_save_argv(int argc, char *const *argv) { ngx_os_argv = (char **) argv; ngx_argc = argc; return NGX_OK; } int main(int argc, char *const *argv){ ngx_save_argv(argc,argv); ngx_init_setproctitle(); ngx_setproctitle("xiejian test"); while(1){ system("ps -ef|awk '$8 ~ /nginx/ {print $0}'"); sleep(10); } return (0); }

运行结果为：