Linux Unix命令确定进程是否正在运行

虽然pidof和pgrep是确定运行什么的好工具，但不幸的是，它们在某些操作系统上都不可用.一个明确的故障保险应该使用以下内容:ps cax | grep command

The output on Gentoo Linux:

14484 ?        S      0:00 apache2
14667 ?        S      0:00 apache2
19620 ?        Sl     0:00 apache2
21132 ?        Ss     0:04 apache2

The output on OS X:

42582   ??  Z      0:00.00 (smbclient)
46529   ??  Z      0:00.00 (smbclient)
46539   ??  Z      0:00.00 (smbclient)
46547   ??  Z      0:00.00 (smbclient)
46586   ??  Z      0:00.00 (smbclient)
46594   ??  Z      0:00.00 (smbclient)

On both Linux and OS X, grep returns an exit code so it's easy to check if the process was found or not:

#!/bin/bash
ps cax | grep httpd > /dev/null
if [ $? -eq 0 ]; then
  echo "Process is running."
else
  echo "Process is not running."
fi

Furthermore, if you would like the list of PIDs, you could easily grep for those as well:

ps cax | grep httpd | grep -o '^[ ]*[0-9]*'

Whose output is the same on Linux and OS X:

3519 3521 3523 3524

The output of the following is an empty string, making this approach safe for processes that are not running:

echo ps cax | grep aasdfasdf | grep -o '^[ ]*[0-9]*'

这种方法适用于编写一个简单的空字符串测试，甚至可以遍历发现的PID.

#!/bin/bash
PROCESS=$1
PIDS=`ps cax | grep $PROCESS | grep -o '^[ ]*[0-9]*'`
if [ -z "$PIDS" ]; then
  echo "Process not running." 1>&2
  exit 1
else
  for PID in $PIDS; do
    echo $PID
  done
fi

您可以通过将其保存到具有执行权限(chmod+x running)的文件(名为"running")并使用参数./running "httpd"执行来测试它

#!/bin/bash
ps cax | grep httpd
if [ $? -eq 0 ]; then
  echo "Process is running."
else
  echo "Process is not running."
fi

WARNING!!!

请记住，您只是在解析ps ax的输出，这意味着，正如在Linux输出中所看到的，它不仅仅是在进程上进行匹配，还包括传递给该程序的参数.我强烈建议在使用此方法时尽可能具体(例如./running "mysql"也将匹配"mysqld"流程).我强烈建议尽可能使用which判断完整路径.

References:

http://linux.about.com/od/commands/l/blcmdl1_ps.htm

http://linux.about.com/od/commands/l/blcmdl1_grep.htm