Shell Commands

These lists will be all over the internet, just lists of commands and what they do. This is just a comprehensive list of the ones that I’ve used or found useful, organized in a manner that works for me.

--help gives information on a command

Directory Commands

• cd = change directory
  • cd directory will move you to a subdirectory
  • use “ “ around the name if it has spaces
  • use forward slashes when moving through multiple subdirectories at a time or changing to a new directory. If you are in /usr cd bin (without a /) will put you in the subdirectory /usr/bin, while cd /bin puts you in /bin a folder outside of /usr
  • cd . will bring you to the directory you are currently in
  • cd .. will move you up one directory for ex. if you’re in /usr/bin/tmp, cd .. moves you to /usr/bin. You can move multiple levels by adding forward slashes ex. cd ../.. moves you to /usr
  • cd - will bring you back to the previous directory
• ls = list
  • lists the files in the current directory, has various options to control the specific output
  • ls -l long format, displaying Unix file types, permissions, number of hard links, owner, group, size, last-modified date and filename
  • ls -a lists all files in the given directory, including those whose names start with “.” which are otherwise hidden
  • ls -R recursively lists subdirectories, for ex. ls -R / would list all files
• mkdir or md = make directory
  • mkdir name_of_directory will create a new sub directory of the current one with the specified name
  • -p the path option, will also create all directories leading up to the desired directory that do not exist already. For ex. mkdir -p a/b will create directory a if it doesn’t exist, then will create subdirectory b
  • -m the mode option, allows you to specify the octal permissions of directories created by mkdir.

File Manipulation

• output redirection
  • Most commands will give their output to the terminal but you can redirect them to a file instead
  • > newfile = create new file or replace file contents with new output
  • >> existingfile = add output of file to existing file
• cat = concatenate
  • reads files sequentially, writing them to standard output, the name comes from its function to concatenate files.
  • cat filename.extension will print the contents of the file to the terminal, you always use the file extension
  • cat file1 file2 will print the concatenation of the two files to the terminal
  • cat > newfile will create a new empty file of the name
• grep = globally search a regular expression and print
  • Given one or more patterns, grep searches input files for matches to the patterns. When it finds a match in a line, it copies the line to standard output (by default), or produces whatever other sort of output you have requested with options.
  • grep [options] [patterns] [file]
• wc = word count
  • reads either standard input or a list of files and generates one or more of the following statistics: newline count, word count, and byte count
  • wc -l <filename> prints the line count (note that if the last line does not have \n, it will not be counted)
  • wc -c <filename> prints the byte count
  • wc -m <filename> prints the character count
  • wc -w <filename> prints the word count

CSV Manipulation

• head = print the header
  • head filename will print the first 10 entries of the file to the terminal
  • head -n 5 filename option n lets you change the number of entries printed, in this case to 5
• cut
  • cut -d , -f 2,4-6 input.csv
  • -d tells cut that columns are separated by commas
  • -f 2,4-6 tells it to extract column 2 and columns 4-6. The -f argument can take a single column number or a comma-separated list of numbers and ranges.