This document gives a brief summary of useful Unix commands. Anything within { and } indicates a user-provided input ({ and } should not be included in the commands).
Documentation and Help
man {command}
manual page for the program
whatis {command}
short description of the program
{command} --help
many programs use the --help flag to print documentation
Listing files
ls
list files in the current directory
ls {path}
list files in the specified path
ls -l {path}
list files in long format (more information)
ls -a {path}
list all files (including hidden files)
Change Directories
cd {path}
change to the specified directory
cd or cd ~
change to the home directory
cd ..
move back one directory
pwd
print working directory. Shows the full path of where you are at the moment (useful if you are lost)
Make or Remove Directories
mkdir {dirname}
create a directory with specified name
rmdir {dirname}
remove a directory (only works if the directory is empty)
rm -r {dirname}
remove the directory and all it’s contents (use with care)
Copy, Move and Remove Files
cp {source/path/file1} {target/path/}
copy “file1” to another directory keeping its name
cp {source/path/file1} {target/path/file2}
copy “file1” to another directory naming it “file2”
cp {file1} {file2}
make a copy of “file1” in the same directory with a new name “file2”
mv {source/path/file1} {target/path/}
move “file1” to another directory keeping its name
mv {source/path/file1} {target/path/file2}
move “file1” to another directory renaming it as “file2”
mv {file1} {file2}
is equivalent to renaming a file
rm {filename}
remove a file
View Text Files
less {file}
view and scroll through a text file
head {file}
print the first 10 lines of a file
head -n {N} {file}
print the first N lines of a file
tail {file}
print the last 10 lines of a file
tail -n {N} {file}
print the last N lines of a file
head -n {N} {file} | tail -n 1
print the Nth line of a file
cat {file}
print the whole content of the file
cat {file1} {file2} {...} {fileN}
concatenate files and print the result
zcat {file} and zless {file}
like cat and less but for compressed files (.zip or .gz)
Find Patterns
Finding (and replacing) patterns in text is a very powerful feature of several command line programs. The patterns are specified using regular expressions (shortened as regex), which are not covered in this document. See this Regular Expressions Cheat Sheet for a comprehensive overview.
grep {regex} {file}
print the lines of the file that have a match with the regular expression pattern
Wildcards
*
match any number of characters
?
match any character only once
Examples
ls sample*
list all files that start with the word “sample”
ls *.txt
list all the files with .txt extension
cp * {another/directory}
copy all the files in the current directory to a different directory
Redirect Output
{command} > {file}
redirect output to a file (overwrites if the file exists)
{command} >> {file}
append output to a file (creates a new file if it does not already exist)
Combining Commands with | Pipes
<command1> | <command2>
the output of “command1” is passed as input to “command2”
Examples
ls | wc -l
count the number of files in a directory
cat {file1} {file2} | less
concatenate files and view them with less
cat {file} | grep "{pattern}" | wc -l
count how many lines in the file have a match with “pattern”