Editing Basic Linux Commands (section)

== Examples ==

=== <span id="ex-pwd"></span>Print Working Directory ===
<syntaxhighlight lang="bash">
pwd
# Output:
# /home/user
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-cd"></span>Change Directory ===
<syntaxhighlight lang="bash">
cd /var/www
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-sed"></span>Substitute Text in String ===
<syntaxhighlight lang="bash">
echo "Hello world" | sed 's/world/Linux/'
# Output:
# Hello Linux
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-ls"></span>List All Files (long + hidden) ===
<syntaxhighlight lang="bash">
ls -la
# Output:
# total 12
# drwxr-xr-x  3 user user 4096 May 16 22:15 .
# drwxr-xr-x 18 user user 4096 May 16 21:00 ..
# -rw-r--r--  1 user user    0 May 16 22:15 index.html
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-mkdir"></span>Create Directory ===
<syntaxhighlight lang="bash">
mkdir backups
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-rmdir"></span>Remove Empty Directory ===
<syntaxhighlight lang="bash">
rmdir backups
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-cp"></span>Copy File ===
<syntaxhighlight lang="bash">
cp secrets.txt /tmp/secrets.bak
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-mv"></span>Move & Rename ===
<syntaxhighlight lang="bash">
mv old.log archive/old.log
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-rm"></span>Force-Delete Directory ===
<syntaxhighlight lang="bash">
rm -rf /tmp/testdir
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-cat"></span>Show File Contents ===
<syntaxhighlight lang="bash">
cat /etc/passwd | grep ":/bin/bash"
# Output:
# root:x:0:0:root:/root:/bin/bash
# user:x:1000:1000:User,,,:/home/user:/bin/bash
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-less"></span>View Large Log ===
<syntaxhighlight lang="bash">
less /var/log/auth.log
# Output:
# (opens file in pager; press q to quit)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-head"></span>First 10 Lines ===
<syntaxhighlight lang="bash">
head -n 10 notes.txt
# Output:
# Line 1
# Line 2
# Line 3
# Line 4
# Line 5
# Line 6
# Line 7
# Line 8
# Line 9
# Line 10
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-tail"></span>Follow File Growth ===
<syntaxhighlight lang="bash">
tail -f /var/log/nginx/access.log
# Output:
# 192.168.1.5 - - [16/May/2025:22:30:01 +0200] "GET / HTTP/1.1" 200 1234
# 192.168.1.5 - - [16/May/2025:22:30:02 +0200] "GET /favicon.ico HTTP/1.1" 404 564
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-grep"></span>Search Pattern ===
<syntaxhighlight lang="bash">
grep -R "passwd" /etc
# Output:
# /etc/login.defs:PASS_MAX_DAYS   99999
# /etc/pam.d/common-password:password requisite pam_pwquality.so retry=3
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-whoami"></span>Current User ===
<syntaxhighlight lang="bash">
whoami
# Output:
# user
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-id"></span>User & Group IDs ===
<syntaxhighlight lang="bash">
id
# Output:
# uid=1000(user) gid=1000(user) groups=1000(user),27(sudo)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-df"></span>Human-Readable Disk Usage ===
<syntaxhighlight lang="bash">
df -h
# Output:
# Filesystem      Size  Used Avail Use% Mounted on
# /dev/sda1        30G   12G   17G  42% /
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-history"></span>Show Last 20 Commands ===
<syntaxhighlight lang="bash">
history | tail -n 20
# Output:
#  981  ls
#  982  cd /var/www
#  983  vim index.html
# ...
# 1000  exit
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-ping"></span>Ping Host 4 Times ===
<syntaxhighlight lang="bash">
ping -c 4 example.com
# Output:
# PING example.com (93.184.216.34) 56(84) bytes of data.
# 64 bytes from 93.184.216.34: icmp_seq=1 ttl=56 time=12.3 ms
# 64 bytes from 93.184.216.34: icmp_seq=2 ttl=56 time=12.1 ms
# 64 bytes from 93.184.216.34: icmp_seq=3 ttl=56 time=12.0 ms
# 64 bytes from 93.184.216.34: icmp_seq=4 ttl=56 time=12.2 ms
# --- example.com ping statistics ---
# 4 packets transmitted, 4 received, 0% packet loss, time 3005ms
# rtt min/avg/max/mdev = 12.012/12.173/12.325/0.123 ms
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-curl"></span>Download Web Page ===
<syntaxhighlight lang="bash">
curl -o index.html http://example.com
# Output:
#   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
#                                  Dload  Upload   Total   Spent    Left  Speed
# 100  1270  100  1270    0     0   2500      0 --:--:-- --:--:-- --:--:--  2500
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-ssh"></span>SSH on Custom Port ===
<syntaxhighlight lang="bash">
ssh -p 2222 user@target
# Output:
# The authenticity of host 'target (192.168.1.50)' can't be established.
# ED25519 key fingerprint is SHA256:abc123...
# Are you sure you want to continue connecting (yes/no/[fingerprint])?
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-man"></span>Read Manual Page ===
<syntaxhighlight lang="bash">
man ssh
# Output:
# (opens manual page; press q to quit)
</syntaxhighlight>
''[[#commands|↑ Commands]]''

=== <span id="ex-echo"></span>Write to File ===
<syntaxhighlight lang="bash">
echo "hacked" > /tmp/proof.txt
# Output:
# (no output)
</syntaxhighlight>
''[[#commands|↑ Commands]]''