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CSC 140: Introduction to IT. UNIX Shells. Objectives. To describe what a UNIX shell is. To describe briefly some commonly used shells. What is a shell?. A command interpreter. Runs external commands like cp and rm . Built-in commands change shell environment: cd – change directory
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CSC 140: Introduction to IT UNIX Shells CIT 140: Introduction to IT
Objectives • To describe what a UNIX shell is. • To describe briefly some commonly used shells CIT 140: Introduction to IT
What is a shell? A command interpreter. • Runs external commands like cp and rm. • Built-in commands change shell environment: • cd – change directory • VAR=value • I/O redirection. • cat /etc/shells >shells • Ease of use • Command line editing, tab completion, history. • Programming • Conditionals, loops, etc. CIT 140: Introduction to IT
Environment Variables CIT 140: Introduction to IT
Shell Initialization Files • Configure shell settings at login. • Create aliases. • Set environment variables. • bash initialization files • /etc/profile System-wide for sh and bash. • /etc/bashrc System-wide for bash. • ~/.bashrc User startup file. CIT 140: Introduction to IT
sh/csh Differences CIT 140: Introduction to IT
Which Shell Suits Your Needs? CIT 140: Introduction to IT
sh/csh Similarities CIT 140: Introduction to IT
How to change your shell? • Change your login shell. > chsh zsh • Run the other shell directly > echo $SHELL /bin/bash > zsh % CIT 140: Introduction to IT
Shell Metacharacters • Non-alphanumeric characters that have special meaning to the shell. • They cannot be used in shell commands. • Allow you to specify multiple files in multiple directories in one command line. CIT 140: Introduction to IT
Globbing • ? Matches any one character. • * Matches zero or more characters. • [] Matches list of characters inside brackets. CIT 140: Introduction to IT
Globbing > ls *html announce.html guidelines.html readings.html sites.html assignments.html index.html schedule.html > cd assignments > ls a[2-3]?html a2.html a3.html CIT 140: Introduction to IT
Command History Up-arrow Previous command Down-arrow Next command history List old commands !! Previous command !# Command # !$ Last arg of previous command CIT 140: Introduction to IT
Command line editing Ctrl-a Beginning of line Ctrl-e End of line Left-arrow Move back one character Right-arrow Move forward one character Ctrl-u Erase line CIT 140: Introduction to IT
Filename completion TAB Completes filename TAB-TAB Show list of possible completions. CIT 140: Introduction to IT
