Comprehensive Linux Command Reference Guide

This document presents a concise reference for frequently used Linux commands, organized by functionality.

File listing and manipulation

ls [options] [directory]
# Example options:
# -a   show all files including hidden ones
# -l   long format with details
# -c   sort by ctime
# --color[=WHEN]   colorize output (never|always|auto)

Moving and renaming files

mv [options] source target
# Options:
# -b   backup before overwriting
# -f   force overwrite without prompting
# -i   interactive, ask before overwriting
# -u   overwrite only if source is newer

Copying files and directories

cp [options] source target
# Options:
# -r, -R   copy directories recursively
# -p       preserve file attributes
# -f       force copy without prompting
# -a       archive mode (preserve all attributes)

Secure copy between hosts

scp [options] source destination
# Options:
# -r       copy directories recursively
# -v       verbose output
# Example:
# scp file.txt user@remote:/path/
# scp -r dir/ user@remote:/path/

Removing files and directories

rm [options] file
# Options:
# -r   remove directories recursively
# -f   force removal without prompts
# -i   interactive, ask before each removal
# -v   verbose output

Creating and updating timestamps

touch [options] file
# Options:
# -a   change only access time
# -m   change only modification time
# -t   specify explicit timestamp (e.g., 202311150930.50)

Navigation commands

pwd          # print current directory
cd [dir]    # change directory (.. for parent, / for root)

Directory management

mkdir [options] dir
# -p   create parent directories as needed
# -m   set directory permissions (e.g., 777)

File inspection and processing

cat [options] file   # display file contents
nl [options] file    # number lines
head [options] file  # show beginning of file
tail [options] file  # show end of file

Searching and pattern matching

grep [options] pattern file
# -c   count matching lines
# -i   case‑insensitive
# -l   list matching file names
# -v   invert match (show non‑matching lines)

Archiving and compression

tar [options] archive files
# -c   create archive
# -x   extract archive
# -z   gzip compression
# -j   bzip2 compression
# -v   verbose listing
# -f   specify archive name

gzip [options] file
# -d   decompress
# -c   write output to stdout
# -#   compression level (1‑9)

System monitoring

ps [options]          # snapshot of current processes
top [options]         # interactive process viewer
free [options]        # memory usage
vmstat                # virtual memory statistics

Network utilities

ifconfig [interface]    # view or configure network interfaces
ping [options] host   # test connectivity
netstat [options]     # network statistics

Scheduling tasks

crontab -e            # edit user crontab
at 12:30               # schedule a one‑time job
watch -n 5 command    # repeat command every 5 seconds

Overall, the guide serves as a quick‑reference cheat‑sheet for system administrators and developers working in a Unix‑like environment.