which命令－查看系统是否安装某工具

我们来看一下 which 命令的 man 手册：


NAME
       which - locate a command

SYNOPSIS
     which [-a] filename ...

DESCRIPTION
     which  returns  the  pathnames of the files which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell.  It does this by searching the PATH for executable files matching the  names of the arguments.

OPTIONS
       -a     print all matching pathnames of each argument

EXIT STATUS
       0      if all specified commands are found and executable

       1      if one or more specified commands is nonexistent or not executable

       2      if an invalid option is specified


可以看到，which 命令是用来定位一个命令的路径的，因此，我们可以使用 which 命令来查看、确认我们的系统是否安装了某一软件工具。