![如何在 Linux 中 grep 帮助输出?](https://linux22.com/image/1264954/%E5%A6%82%E4%BD%95%E5%9C%A8%20Linux%20%E4%B8%AD%20grep%20%E5%B8%AE%E5%8A%A9%E8%BE%93%E5%87%BA%EF%BC%9F.png)
当我使用命令中不存在的开关时,lsof
会ps
返回一个冗长的帮助菜单。我不想阅读整个内容,而是希望能够在其中 grep 查找我要查找的开关。我宁愿不使用两个命令。
这是我尝试 grep 时得到的结果:
ubuntu@ubuntu:~$ lsof -h | grep "\-U"
lsof 4.81
latest revision: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/
latest FAQ: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/FAQ
latest man page: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/lsof_man
usage: [-?abhlnNoOPRtUvVX] [+|-c c] [+|-d s] [+D D] [+|-f[gG]]
[-F [f]] [-g [s]] [-i [i]] [+|-L [l]] [+m [m]] [+|-M] [-o [o]] [-p s]
[+|-r [t]] [-s [p:s]] [-S [t]] [-T [t]] [-u s] [+|-w] [-x [fl]] [--] [names]
Defaults in parentheses; comma-separated set (s) items; dash-separated ranges.
-?|-h list help -a AND selections (OR) -b avoid kernel blocks
-c c cmd c ^c /c/[bix] +c w COMMAND width (9)
+d s dir s files -d s select by FD set +D D dir D tree *SLOW?*
-i select IPv[46] files -l list UID numbers
-n no host names -N select NFS files -o list file offset
-O avoid overhead *RISK -P no port names -R list paRent PID
-s list file size -t terse listing -T disable TCP/TPI info
-U select Unix socket -v list version info -V verbose search
+|-w Warnings (+) -X skip TCP&UDP* files -- end option scan
+f|-f +filesystem or -file names +|-f[gG] flaGs
-F [f] select fields; -F? for help
+|-L [l] list (+) suppress (-) link counts < l (0 = all; default = 0)
+m [m] use|create mount supplement
+|-M portMap registration (-) -o o o 0t offset digits (8)
-p s exclude(^)|select PIDs -S [t] t second stat timeout (15)
-T qs TCP/TPI Q,St (s) info
-g [s] exclude(^)|select and print process group IDs
-i i select by IPv[46] address: [46][proto][@host|addr][:svc_list|port_list]
+|-r [t[m<fmt>]] repeat every t seconds (15); + until no files, - forever.
An optional suffix to t is m<fmt>; m must separate t from <fmt> and
<fmt> is an strftime(3) format for the marker line.
-s p:s exclude(^)|select protocol (p = TCP|UDP) states by name(s).
-u s exclude(^)|select login|UID set s
-x [fl] cross over +d|+D File systems or symbolic Links
names select named files or files on named file systems
Anyone can list all files; /dev warnings disabled; kernel ID check disabled.
答案1
您的 grep 不起作用,因为帮助输出大多数时候都会刷新到标准错误输出 (stderr)。
此流具有文件描述符 2 而不是 1,并且管道命令重定向文件描述符 1。解决此问题的一种方法是将错误输出重定向到标准输出:
lsof -h 2>&1 | grep "\-U"