which命令

查找命令的绝对路径

[bestcoder@localhost test1]$ which touch 
/usr/bin/touch

whereis命令

查找命令的帮助文档的绝对路径

[bestcoder@localhost test1]$ whereis touch
touch: /usr/bin/touch /usr/share/man/man1/touch.1.gz /usr/share/man/man1p/touch.1p.gz