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This article mainly shows you "what are the infrequently used Linux commands", the content is simple and easy to understand, and the organization is clear. I hope it can help you solve your doubts. Let Xiaobian lead you to study and learn "what are the infrequently used Linux commands".

1）pgrep

pgrep has a p in front of it, which we can guess is process-related, grep again, and of course this is process-related grep. However, this command is mainly used to enumerate process IDs. For example:

The code is as follows:

$ pgrep -u hchen

22441

22444

This command is equivalent to:

The code is as follows:

ps -ef | egrep '^hchen' | awk '{print $2}'

2）pstree

This command lists processes in a tree form. As follows:

The code is as follows:

[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

This command is mainly to do a relatively high precision mathematical operations. Such as square root. Here is a script we wrote using bc command (filename: sqrt)

The code is as follows:

#!/ bin/bash

if [ $# -ne 1 ]

then

echo 'Usage: sqrt number'

exit 1

else

echo -e "sqrt($1)\nquit\n" | bc -q -i

fi

So we can use this script for square root operations like this:

The code is as follows:

[hchen@RHELSVR5]$ ./ sqrt 36

6

[hchen@RHELSVR5]$ ./ sqrt 2.0000

1.4142

[hchen@RHELSVR5]$ ./ sqrt 10.0000

3.1622

4）split

If you have a large file and you want to split it into smaller files, this command is the one to do it.

The code is as follows:

[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

File merging requires only simple merging, such as:

The code is as follows:

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

5）nl

The nl command is similar to cat except that it has line numbers. As follows:

The code is as follows:

[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

Anyone familiar with Unix should know that this is a system call or command to create a named pipe. Usually, we use vertical bars on the command line."|"Stringing orders together is using a life-less pipeline. And we use mkfifo to use the named pipe. Here is an example:

Here's how to create a named pipe:

The code is as follows:

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

[hchen@RHELSVR5 ~]# ls -l /tmp

prw-rw-r-- 1 hchen hchen 0 05-10 18:58 hchenpipe

Then, we run the following command in a shell that doesn't return unless someone reads information from the named pipe.

The code is as follows:

[hchen@RHELSVR5 ~]# ls -al > /tmp/hchenpipe

We read the information in this pipe in another command window: (which causes the previous command to return)

The code is as follows:

[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

This command tells you which DLL is used by an executable file. For example:

The code is as follows:

[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

This command allows you to convert a man file to a plain text file. The following example:

The code is as follows:

# PAGER=cat

# man less | col -b > less.txt

9）xmlwf

This command lets you check whether all tags in an XML document are correct. For example:

The code is as follows:

[hchen@RHELSVR5 ~]# curl 'http://cocre.com/? 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

You can list open files.

The code is as follows:

[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)

The above is "What are the infrequently used Linux commands?" All the contents of this article, thank you for reading! I believe that everyone has a certain understanding, hope to share the content to help everyone, if you still want to learn more knowledge, welcome to pay attention to the industry information channel!

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