10 Essential Linux Commands Every Developer Should Master

01 pgrep

The pgrep command lists process IDs matching given criteria, similar to combining ps, egrep, and awk.

$ pgrep -u hchen22441 22444

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

02 pstree

pstree

displays the process hierarchy in a tree format, making it easy to visualize parent‑child relationships among running processes.

[hchen@RHELSVR5 ~]$ pstree
init-+-acpid
     |-auditd-+-python
     |        `-{auditd}
     |-automount---4*[{automount}]
     |-backup.sh---sleep
     |-dbus-daemon
     |-httpd---10*[httpd]
     ... (truncated for brevity)

03 bc

bc

is an arbitrary‑precision calculator useful for mathematical operations such as computing square roots. The example script sqrt demonstrates its use.

#!/bin/bash
if [ $# -ne 1 ]; then
    echo 'Usage: sqrt number'
    exit 1
else
    echo -e "sqrt($1)
quit
" | bc -q -i
fi

Running the script:

[hchen@RHELSVR5]$ ./sqrt 36
6
[hchen@RHELSVR5]$ ./sqrt 2.0000
1.4142
[hchen@RHELSVR5]$ ./sqrt 10.0000
3.1622

04 split

split

divides a large file into smaller chunks of a specified size.

[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
... (additional parts) ...

Recombine the parts:

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

05 nl

The nl command numbers lines of a file, similar to cat -n, but with more formatting options.

[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,

06 mkfifo

mkfifo

creates a named pipe, allowing inter‑process communication via a file in the filesystem.

[hchen@RHELSVR5 ~]# mkfifo /tmp/hchenpipe
[hchen@RHELSVR5 ~]# ls -l /tmp
prw-rw-r-- 1 hchen hchen 0 05-10 18:58 hchenpipe

One shell writes to the pipe (blocks until read): [hchen@RHELSVR5 ~]# ls -al > /tmp/hchenpipe Another shell reads from it, releasing the block:

[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 ..
... (listing continues) ...

07 ldd

ldd

shows the shared libraries required by an executable.

[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)
... (additional libraries) ...

08 col

col

filters reverse line feeds, often used to convert man pages to plain text.

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

09 xmlwf

xmlwf

validates an XML file, reporting mismatched tags or other well‑formedness errors.

[hchen@RHELSVR5 ~]# curl 'https://coolshell.cn/?feed=rss2' > cocre.xml
[hchen@RHELSVR5 ~]# xmlwf cocre.xml
[hchen@RHELSVR5 ~]# perl -i -pe 's@<link>@<br>@g' cocre.xml
[hchen@RHELSVR5 ~]# xmlwf cocre.xml
cocre.xml:13:23: mismatched tag

10 lsof

lsof

lists open files and the processes that opened them, useful for diagnosing resource usage.

[root@RHELSVR5 ~]# lsof | grep TCPhttpd
548    apache    4u   IPv6 14300967 TCP *:http (LISTEN)
... (additional entries) ...