6 useful Linux commands that you may not be familiar with!
Linux is a powerful operating system. This article has collected 6 Linux commands that you may not have used, but they are quite useful for your reference.
1）bc
This Linux command is used for mathematical operations with higher precision. Such as: taking the square root and so on. Now use the bc command to write a script (file name: sqrt)
#!/bin/bash
if [ $
then
echo 'Usage: sqrt number'
exit 1
else
echo -e "sqrt($1)\nquit\n" | bc -q -i
fi
Then, you can use this script to perform square root operations:
[hchen@RHELSVR5]$ ./sqrt 36
6
[hchen@RHELSVR5]$ ./sqrt 2.0000
1.4142
[hchen@RHELSVR5]$ ./sqrt 10.0000
3.1622
2）split
If your file is large, but you receive an order to split it into small files, then this command comes in handy.
[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
On the contrary, merging only requires simple merging, such as:
[hchen@RHELSVR5]# cat LF_* >largefile.tar.gz
3）pgrep
There is a p before the name of pgrep. It can be guessed that it may be related to grep. Indeed, this is a process-related grep command. However, this command is mainly used to list the process ID. Such as:
$ pgrep -u hchen
22441
22444
This command is equivalent to:
ps -ef | egrep '^hchen' | awk '{print $2}'
4）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 © 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,
5）ldd
这个命令，用来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)
6）col
这个命令，能将man文件转成纯文本文件。如下示例：
PAGER=cat # man less | col -b > less.txt
Have you ever used these 6 Linux commands? Welcome to leave a message and exchange!
Need C/C++ Linux advanced server architect learning materials plus group 960994558 to obtain (including C/C++, Linux, golang technology, Nginx, ZeroMQ, MySQL, Redis, fastdfs, MongoDB, ZK, streaming media, CDN, P2P, K8S, Docker , TCP/IP, coroutine, DPDK, ffmpeg, etc.)
