run-parts(8) 实用程序的目的

Question

至少在基于 Debian 的系统下，debianutils包中有一个run-parts实用程序，可用于各种脚本。例如在 /etc/X11/Xsession.conf 中。它将运行在目录中找到的所有可执行文件。为什么需要运行部件而可以与选项或实用程序一起使用？另外，什么是可执行文件？看起来它不是简单地检查文件权限：find-permtestrun-parts

# run-parts --list --lsbsysinit /etc/X11/Xsession.d | tail -1
/etc/X11/Xsession.d/90x11-common_ssh-agent
# ls -l /etc/X11/Xsession.d/90x11-common_ssh-agent
-rw-r--r-- 1 root root 629 2010-11-02 23:17 /etc/X11/Xsession.d/90x11-common_ssh-agent
# head /etc/X11/Xsession.d/90x11-common_ssh-agent
# $Id: 90x11-common_ssh-agent 305 2005-07-03 18:51:43Z dnusinow $

# This file is sourced by Xsession(5), not executed.

STARTSSH=
SSHAGENT=/usr/bin/ssh-agent
SSHAGENTARGS=

if has_option use-ssh-agent; then
  if [ -x "$SSHAGENT" ] && [ -z "$SSH_AUTH_SOCK" ] \
# 

Answer 1

您可以使用find代替run-parts，无法显示哪个更好。但我认为 usingrun-parts更短（更少输入）并使您的脚本更易于维护。一个例子是/etc/crontab：

# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# m h dom mon dow user  command
17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly
25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

对于第二个问题，您可以在debianutils源代码中找到答案。在文件中run-parts.c，第 198 行：

/* Execute a file */                                                            
void run_part(char *progname)                                                   
{ 
     ....
     args[0] = progname;                                                         
     execv(progname, args);                                                      
     error("failed to exec %s: %s", progname, strerror(errno));                  
     exit(1);
     ....
}

你可以看到run-parts使用execv系统调用。因此，如果您的文件不是二进制可执行文件或Interpreter script，execv则无法运行该文件。

笔记

• 什么是Interpreter script：

从man execve, 部分Interpreter scripts:

Interpreter scripts
       An  interpreter  script  is  a  text  file  that has execute permission
       enabled and whose first line is of the form:

           #! interpreter [optional-arg]

       The interpreter must be a valid pathname for an executable which is not
       itself  a  script.   If  the filename argument of execve() specifies an
       interpreter script, then interpreter will be invoked with the following
       arguments:

           interpreter [optional-arg] filename arg...

       where arg...  is the series of words pointed to by the argv argument of
       execve().

       For portable use, optional-arg should either be absent, or be specified
       as  a  single word (i.e., it should not contain white space); see NOTES
       below.

• 您可以在此处查看 debianutils 源代码。