$ pgrep -u hchen2244122444
这个命令相当于：
ps -ef | egrep '^hchen' | awk '{print $2}'这个命令可以以树形的方式列出进程。如下所示：
[hchen@RHELSVR5 ~]$ pstreeinit-+-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 [ $# -ne 1 ]
then
echo 'Usage: sqrt number'
exit 1else
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
[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
<span style="outline: 0px;font-size: 15px;">nl</span>命令其它和<span style="outline: 0px;font-size: 15px;">cat</span>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,
[hchen@RHELSVR5 ~]# mkfifo /tmp/hchenpipe [hchen@RHELSVR5 ~]# ls -l /tmpprw-rw-r-- 1 hchen hchen 0 05-10 18:58 hchenpipe
[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/hchenpipedrwx------ 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
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)
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
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 Speed100 64882 0 64882 0 0 86455 0 --:--:-- --:--:-- --:--:-- 2073k[hchen@RHELSVR5 ~]# xmlwf cocre.xml[hchen@RHELSVR5 ~]# perl -i -pe 's@<link>@<br>@g' cocre.xml[hchen@RHELSVR5 ~]# xmlwf cocre.xmlcocre.xml:13:23: mismatched tag
可以列出打开了的文件。
[root@RHELSVR5 ~]# lsof | grep TCPhttpd 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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