十个你可能不曾用过的Linux命令

下面可能是你不曾用过后十个Linux的命令。相当的有用。

1)pgrep
pgrep名字前有个p,我们可以猜到这和进程相关,又是grep,当然这是进程相关的grep命令。不过,这个命令主要是用来列举进程ID的。如:

$ pgrep -u hchen
22441
22444
这个命令相当于:

ps -ef | egrep ‘^hchen’ | awk ‘{print $2}’
2)pstree
这个命令可以以树形的方式列出进程。如下所示:
[hchen@RHELSVR5 ~]$ pstree
init-+-acpid
|-auditd-+-python
| `-{auditd}
|-automount—4*[{automount}]
|-backup.sh—sleep
|-dbus-daemon
|-events/0
|-events/1
|-hald—hald-runner—hald-addon-acpi
|-httpd—10*[httpd]
|-irqbalance
|-khelper
|-klogd
|-ksoftirqd/0
|-ksoftirqd/1
|-kthread-+-aio/0
| |-aio/1
| |-ata/0
| |-ata/1
| |-ata_aux
| |-cqueue/0
| |-cqueue/1
| |-kacpid
| |-kauditd
| |-kblockd/0
| |-kblockd/1
| |-kedac
| |-khubd
| |-6*[kjournald]
| |-kmirrord
| |-kpsmoused
| |-kseriod
| |-kswapd0
| |-2*[pdflush]
| |-scsi_eh_0
| |-scsi_eh_1
| |-xenbus
| `-xenwatch
|-migration/0
|-migration/1
|-6*[mingetty]
|-3*[multilog]
|-mysqld_safe—mysqld—9*[{mysqld}]
|-smartd
|-sshd—sshd—sshd—bash—pstree
|-svscanboot—svscan-+-3*[supervise—run]
| |-supervise—qmail-send-+-qmail-clean
| | |-qmail-lspawn
| | `-qmail-rspawn
| `-2*[supervise—tcpserver]
|-syslogd
|-udevd
|-watchdog/0
|-watchdog/1
`-xinetd

3)bc
这个命令主要是做一个精度比较高的数学运算的。比如开平方根等。下面是一个我们利用bc命令写的一个脚本(文件名:sqrt)
#!/bin/bash

if [ $
then
echo ‘Usage: sqrt number’
exit 1
else
echo -e “sqrt($1)\nquit\n” | bc -q -i
fi
于是,我们可以这样使用这个脚本进行平方根运算:
[hchen@RHELSVR5]$ ./sqrt 36
6
[hchen@RHELSVR5]$ ./sqrt 2.0000
1.4142
[hchen@RHELSVR5]$ ./sqrt 10.0000
3.1622
4)split
如果你有一个很大的文件,你想把其分割成一些小的文件,那么这个命令就是干这件事的了。
[hchen@RHELSVR5 applebak]# ls -l largefile.tar.gz
-rw-r–r– 1 hchen hchen 436774774 04-17 02:00 largefile.tar.gz

[hchen@RHELSVR5 applebak]# split -b 50m largefile.tar.gz LF_

[hchen@RHELSVR5]# ls -l LF_*
-rw-r–r– 1 hchen hchen 52428800 05-10 18:34 LF_aa
-rw-r–r– 1 hchen hchen 52428800 05-10 18:34 LF_ab
-rw-r–r– 1 hchen hchen 52428800 05-10 18:34 LF_ac
-rw-r–r– 1 hchen hchen 52428800 05-10 18:34 LF_ad
-rw-r–r– 1 hchen hchen 52428800 05-10 18:34 LF_ae
-rw-r–r– 1 hchen hchen 52428800 05-10 18:35 LF_af
-rw-r–r– 1 hchen hchen 52428800 05-10 18:35 LF_ag
-rw-r–r– 1 hchen hchen 52428800 05-10 18:35 LF_ah
-rw-r–r– 1 hchen hchen 17344374 05-10 18:35 LF_ai
文件合并只需要使用简单的合并就行了,如:

[hchen@RHELSVR5]# cat LF_* >largefile.tar.gz
5)nl

nl命令其它和cat命令很像,只不过它会打上行号。如下所示:
[hchen@RHELSVR5 include]# nl stdio.h | head -n 10
1 /* Define ISO C stdio on top of C++ iostreams.
2 Copyright (C) 1991,1994-2004,2005,2006 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.

4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.

8 The GNU C Library is distributed in the hope that it will be useful,
6)mkfifo

熟悉Unix的人都应该知道这个是一个创建有名管道的系统调用或命令。平时,我们在命令行上使用竖线“|”把命令串起来是使用无命管道。而我们使用mkfifo则使用的是有名管道。下面是示例:

下面是创建一个有名管道:

[hchen@RHELSVR5 ~]# mkfifo /tmp/hchenpipe

[hchen@RHELSVR5 ~]# ls -l /tmp
prw-rw-r– 1 hchen hchen 0 05-10 18:58 hchenpipe
然后,我们在一个shell中运行如下命令,这个命令不会返回,除非有人从这个有名管道中把信息读走。
[hchen@RHELSVR5 ~]# ls -al > /tmp/hchenpipe
我们在另一个命令窗口中读取这个管道中的信息:(其会导致上一个命令返回)
[hchen@RHELSVR5 ~]# head /tmp/hchenpipe
drwx—— 8 hchen hchen 4096 05-10 18:27 .
drwxr-xr-x 7 root root 4096 03-05 00:06 ..
drwxr-xr-x 3 hchen hchen 4096 03-01 18:13 backup
-rw——- 1 hchen hchen 721 05-05 22:12 .bash_history
-rw-r–r– 1 hchen hchen 24 02-28 22:20 .bash_logout
-rw-r–r– 1 hchen hchen 176 02-28 22:20 .bash_profile
-rw-r–r– 1 hchen hchen 124 02-28 22:20 .bashrc
-rw-r–r– 1 root root 14002 03-07 00:29 index.htm
-rw-r–r– 1 hchen hchen 31465 03-01 23:48 index.php
7)ldd
这个命令可以知道你的一个可执行文件所使用了动态链接库。如:

[hchen@RHELSVR5 ~]# ldd /usr/bin/java
linux-gate.so.1 => (0x00cd9000)
libgij.so.7rh => /usr/lib/libgij.so.7rh (0x00ed3000)
libgcj.so.7rh => /usr/lib/libgcj.so.7rh (0x00ed6000)
libpthread.so.0 => /lib/i686/nosegneg/libpthread.so.0 (0x00110000)
librt.so.1 => /lib/i686/nosegneg/librt.so.1 (0x009c8000)
libdl.so.2 => /lib/libdl.so.2 (0x008b5000)
libz.so.1 => /usr/lib/libz.so.1 (0x00bee000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00aa7000)
libc.so.6 => /lib/i686/nosegneg/libc.so.6 (0x0022f000)
libm.so.6 => /lib/i686/nosegneg/libm.so.6 (0x00127000)
/lib/ld-linux.so.2 (0x00214000)
8)col

这个命令可以让你把man文件转成纯文本文件。如下示例:

# PAGER=cat
# man less | col -b > less.txt
9)xmlwf

这个命令可以让你检查一下一个XML文档是否是所有的tag都是正常的。如:

[hchen@RHELSVR5 ~]# curl ‘https://coolshell.cn/?feed=rss2’ > cocre.xml
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 64882 0 64882 0 0 86455 0 –:–:– –:–:– –:–:– 2073k
[hchen@RHELSVR5 ~]# xmlwf cocre.xml
[hchen@RHELSVR5 ~]# perl -i -pe ‘s@@
@g’ cocre.xml
[hchen@RHELSVR5 ~]# xmlwf cocre.xml
cocre.xml:13:23: mismatched tag
10)lsof
可以列出打开了的文件。
[root@RHELSVR5 ~]# lsof | grep TCP
httpd 548 apache 4u IPv6 14300967 TCP *:http (LISTEN)
httpd 548 apache 6u IPv6 14300972 TCP *:https (LISTEN)
httpd 561 apache 4u IPv6 14300967 TCP *:http (LISTEN)
httpd 561 apache 6u IPv6 14300972 TCP *:https (LISTEN)
sshd 1764 root 3u IPv6 4993 TCP *:ssh (LISTEN)
tcpserver 8965 root 3u IPv4 153795500 TCP *:pop3 (LISTEN)
mysqld 10202 mysql 10u IPv4 73819697 TCP *:mysql (LISTEN)
sshd 10735 root 3u IPv6 160731956 TCP 210.51.0.232:ssh->123.117.239.68:31810 (ESTABLISHED)
sshd 10767 hchen 3u IPv6 160731956 TCP 210.51.0.232:ssh->123.117.239.68:31810 (ESTABLISHED)
vsftpd 11095 root 3u IPv4 152157957 TCP *:ftp (LISTEN)

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