2

getenv() in my C++ apache/cgi gives me weird things, then I checked the environ inside /proc/${PID_OF_THE_RUNNING_PROCESS}, they did not match, which I think they should, I am wondering what was wrong with /proc or it was getenv()?

shell@kernel # xargs --null --max-args=1 echo < /proc/${PID_OF_THE_RUNNING_PROCESS}/environ 
PATH=/usr/bin:/bin:/usr/sbin:/sbin
LD_LIBRARY_PATH=/usr/local/httpd-2.2.19/lib:

Code of PID_OF_THE_RUNNING_PROCESS

#include<stdio.h>
extern char **environ;

void run()
{
    char* s = *environ;
    printf("declare -x  all env begin\n");    
    for (int i = 1; NULL != s; ++i) {
        printf("declare -x  %s\n", s);
        s = *(environ+i);
    }
    printf("declare -x  all env end\n");
}

Console log of PID_OF_THE_RUNNING_PROCESS

declare -x  all env begin
declare -x  FCGI_ROLE=RESPONDER
declare -x  UNIQUE_ID=Wvq-Cn8AAAEAAAkmJlsAAAmM
declare -x  HTTP_HOST=www.example.com
declare -x  HTTP_X_CLIENT_PROTO=https
declare -x  HTTP_X_CLIENT_PROTO_VER=HTTP/1.1
declare -x  HTTP_X_REAL_IP=112.96.194.222
declare -x  HTTP_X_FORWARDED_FOR=112.96.194.222
declare -x  CONTENT_LENGTH=177
declare -x  HTTP_CHARSET=utf-8
declare -x  HTTP_ACCEPT_ENCODING=gzip
declare -x  HTTP_REFERER=https://serviceexample.com/exbb58374cdce267a6/91/page-frame.html
declare -x  CONTENT_TYPE=application/x-www-form-urlencoded
declare -x  HTTP_USER_AGENT=Mozilla/5.0 (Linux; Android 5.1; vivo X6Plus D Build/LMY47I; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/57.0.2987.132 MQQBrowser/6.2 TBS/044030 Mobile Safari/537.36 MicroMessenger/6.6.6.1300(0x26060637) NetType/4G Language/zh_CN MicroMessenger/6.6.6.1300(0x26060637) NetType/4G Language/zh_CN
declare -x  PATH=/usr/bin:/bin:/usr/sbin:/sbin
declare -x  SERVER_SIGNATURE=
declare -x  SERVER_SOFTWARE=Apache/2.2.19 (Unix) mod_ssl/2.2.19 OpenSSL/1.0.1t DAV/2 mod_fcgid/2.3.9
declare -x  SERVER_NAME=www.example.com
declare -x  SERVER_ADDR=10.241.94.209
declare -x  SERVER_PORT=80
declare -x  REMOTE_ADDR=10.56.81.214
declare -x  DOCUMENT_ROOT=/data/doc/www.example.com/htdocs
declare -x  SERVER_ADMIN=webmaster@tencent.com
declare -x  SCRIPT_FILENAME=/data/doc/www.example.com/cgi-bin/ex/common/www_ex_time.cgi
declare -x  REMOTE_PORT=46151
declare -x  GATEWAY_INTERFACE=CGI/1.1
declare -x  SERVER_PROTOCOL=HTTP/1.1
declare -x  REQUEST_METHOD=POST
declare -x  QUERY_STRING=
declare -x  REQUEST_URI=/cgi-bin/ex/common/www_ex_time.cgi
declare -x  SCRIPT_NAME=/cgi-bin/ex/common/www_ex_time.cgi
declare -x  HTTP_CONNECTION=close
declare -x  all env end
declare -x  112.96.194.222
4

2 回答 2

2

是的，我找到了答案，如果在运行时更改了 env，它们是不一样的。我在这里
找到了官方文档： 

/proc/[pid]/environ
              This file contains the initial environment that was set when
              the currently executing program was started via execve(2).              
              ......
              If, after an execve(2), the process modifies its environment
              (e.g., by calling functions such as putenv(3) or modifying the
              environ(7) variable directly), this file will not reflect
              those changes.

启动时请注意初始环境 我们将环境更改为，例如，这将反映，我们可以通过验证它，但是/proc/self/environ，它们是静态的，在运行时不会受到影响。
setenv()extern environ

于 2018-05-16T03:06:31.790 回答
1

/ proc/$pid/environ数据显示进程启动时环境变量的状态。如果环境变量随后被修改（例如， via putenv()），这将反映在getenv()但不是/proc/$pid/environ的返回值中。您可以通过在一个终端中编译和运行以下程序并在另一个终端中查看它的 proc/.../environ 来看到这一点。

#include <stdio.h>
#include <stdlib.h>

int main() {
    putenv("HOME=WTF");
    char *home = getenv("HOME");
    printf("pid %d  HOME=%s\n", getpid(), home);
    sleep(300);
}

PS，理论上对环境的更新可以反映在/proc/$pid/environ中，但实际上我不知道有任何这样做的实现。

于 2018-05-16T03:08:04.127 回答