b-duncs / holbertonschool-system_engineering-devops

Introduction to Shell

holberton-system_engineering-devops

0x00. Shell, basics

man or help

• cd: change directory
• ls: list directory contents
• pwd: print name of current working directory
• less: view file contents
• file: determine file types
• ln: create hard and symbolic links
• cp: copy file and directories
• mv: move/rename files and directories
• rm: remove files and directories
• mkdir: create directories
• type: indicate how a command line name is interpreted
• which: display which executable program will be executed
• help: get help for shell builtins
• man: display a command's manual page

0x01. Shell, permissions

man or help

• chmod: change a file's mode
• sudo: execute a command as another user
• su: return a shell as another user
• chown: change a file's owner
• chgrp: change a file's group owner
• id: display the user identity
• groups: print the groups a user is in
• whoami: print effective userid
• adduser: creates a new user in the system
• useradd: creates a new user
• addgroup: creates a new group in the system

0x02. Shell, I/O redirections and filters

man or help

• echo: display a line of text
• cat: concatenate files
• head: output the first part of a file
• tail: output the last part of a file
• find: search for files in a directory hierarchy
• wc: print newline, word, and byte counts for each file
• sort: sort lines of text
• uniq: report or omit repeated lines
• grep: print lines matching a pattern
• tr: translate or delete characters
• rev: reverse lines characterwise
• cut: remove sections from each line of files
• passwd (5) (i.e. man 5 passwd): passwd - password file

0x03. Shell, init files, variables, and expansions

man or help

• printenv: print all or part of environment
• set: set or unset options and positional parameters
• unset: unset values and attributes of variables and functions
• export: set the export attribute for variables
• alias: define or display aliases
• unalias: remove alias definitions
• .: execute commands in the current environment
• source: contains sample profile files for general or individual use
• printf: format and print data

0x04. Shell, loops, conditions, and parsing

man or help

• env: run a program in a modified environment
• cut: remove sections from each line of files
• for: repeatedly execute a set of commands for every element present
• while: repeatedly execute a set of commands as long as the COMMAND returns true
• until: executes a set of commands as long as the final command has an exit status which is not zero
• if: executes commands based on conditions

0x05. Shell, processes and signals

man or help

• ps: report a snapshot of the current processes
• pgrep: looks through the currently running processes and lists the process IDS which match the selection criteria to stdout
• pkill: will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout
• kill: terminate a process
• exit: cause normal process termination
• trap: trap signals