Library Carpentry: The UNIX Shell: Reference

Key Points

What is the shell?
  • The shell is powerful

  • The shell can be used to copy, move, and combine multiple files

Navigating the filesystem
  • Knowing where you are in your directory structure is key to working with the shell

Working with files and directories
  • The shell can be used to copy, move, and combine multiple files

Automating the tedious with loops
  • Looping is the foundation for working smarter with the command line

  • Loops help us to do the same (or similar) things to a bunch of items

Counting and mining with the shell
  • The shell can be used to count elements of documents

  • The shell can be used to search for patterns within files

  • Commands can be used to count and mine any number of files

  • Commands and flags can be combined to build complex queries specific to your work

Working with free text
  • Shell tools can be combined to powerful effect

Shell Cheat Sheet


Shell: Basics

pwd - print working directory

man - display the user manual

history - displays the history list with line numbers, use n to limit the list

ls - list contents of a directory

cd change directory

cd pathname - takes you to the directory specified by pathname

cd ~ - takes you to your home directory

cd .. - takes you up one directory


Shell: Interacting with Files

mkdir make a directory

cat print to shell or send file or files to output

head output first 10 lines of a file or files

tail output last 10 lines of a file or files

mv rename or move a file or files. Syntax for renaming a file: mv FILENAME NEWFILENAME

cp make a backup copy of a file or files. Syntax: cp FILENAME NEWFILENAME

> redirect output. Syntax with cat: cat FILENAME1 FILENAME2 > NEWFILENAME

>> redirect output by appending to the filename specified. Syntax with cat: cat FILENAME1 FILENAME2 >> NEWFILENAME

rm remove a file or files. NB: USE WITH EXTREME CAUTION!!!

rmdir -r will delete a directory, even if it is not empty.

rm -ri will delete a directory, even if it is not empty, but will ask you to confirm each deletion.

touch will update timestamp information on files. __

Shell: Wildcards

? a placeholder for one character or number

* a placeholder for zero or more characters or numbers

[] defines a class of characters

Examples


Shell: Counting and Mining

wc word count

sort sort input

grep global regular expression print


Shell: Working with Free Text

sed is used to modify files, use -e flag to run multiple commands

tr translates or deletes characters in a file

'''\n translates every blank space into \n, then renders on a new line

uniq reports or filters repeated lines in a file, use with -c to do a word count of the duplicates