Linux and Unix file names, including command line operations

linuxAndUnixFileNamed.md

#Linux and Unix files and directories at the command line

The same rules apply to file names and directory names, but conventions vary a bit. For example, file names often have extensions, but directory names seldom do.

File Names

File names that start with a period . are "hidden" files

A good set of guidelines is at https://www.cyberciti.biz/faq/linuxunix-rules-for-naming-file-and-directory-names/

Summary of the key points:

• File names are case sensitive.
  • lowercase and camelCase are common
  • They can be long, but keep them short if possible
  • Avoid blanks if possible
  • If you encounter a name with a blank or a troublesome special character
    • Use a backslash followed by a space for blanks For example: my\ file
    • Enclose the entire file name in " or ' marks. Similar rules to php. " allows for variable expansion echo 'My path is $PATH' echo "My path is $PATH"

Extensions

Some file (and directory) names have extensions. This is a period followed by a few letters

Some common extensions in linux

• .txt A text file
• .tar A group of files combined into a single file. Also called an "archive"
• .gz, *.bz A compressed file
• .tar.gz An archive that has also been compressed (like a zip)
• .zip A compressed archive that is mostly compatable with windows zip files
• .sh A "shell script" or miniature program

commands

• ls List the files
• ls -l Give a long, or detailed listing of files
• ls -a List all files, including hidden files
• ls -al Give a long listing of all files
• ls -d give a directory listing
• touch Create a file
• rm Remove a file
• cd Change directory
• mkdir Create a directory
• rmdir Remove an empty directory
• rm -r Recursively remove all files and subdirectories

Showing text files

• cat filename -- Short for "contatinate." It lists the entire file. Long files will scroll off the screen

• less filename -- Shows the file a line at a screen at a time. *Page Up and Page down keys work. Spacebar is like Page Down. Up and down arrows move one line at a time. q to exit.

• nano filename Edits a file. ^ means "Ctrl"

• head filename -- Shows the first 10 lines "head -n 5 filename " would print 5 lines

• tail filename -- prints the end of the list

• lp filename -- Sends the file to a printer, if a printer is set up.

Other miscellaneous commands

• man commandname Help file
• exit -- Exits from the browser.
• cp sourse destination Copies from a file to a file. The second argument has to be supplied. The second argument can be a filename or a directory name. Often you want to copy to the current directory, so use a period as the second argument. You might do something like cp ../data.txt .
• mv *source destination Moves a file. It works like cp. mv can also be used to rename files

Home and special folder symbols

/home/username is your "home" folder

~ (tilde) is a shorthand for "home . is the current directory .. is the parent directory. ../.. would be the "grandparent" directory

Command Line special characters

• ^c "Break"
• ^d Endo of file
• ; Put another command on the same line, and always execute the second command
• && Put another command on the same line, but only execute the second command if the first command is successfule
• Execute the command in the background. You wwill most commonly use this if you launch a gui app from the command line. But be careful because closing the terminal will also abort the gui program without warning.

• Redirect output to a file

• < Redirect input from a file
• | "Pipe" the output of one command as input to the next command. For example cat someFile | sort | less