High Energy Physics

More Shell Features

Process Control

• An & at the end of a command line will run the command as a background process
• Typing <Ctrl-Z> will stop a foreground process
• Typing <Ctrl-C> will (usually) kill a foreground process
• A stopped process may be made to run in the background by typing bg
• A background or stopped process may be brought to the foreground by the fg command.
• jobs displays all background and suspended processes of the current shell
• kill will kill a process using the number returned by jobs or the process ID (found with the ps command)

I/O redirection

• To capture output from a command, redirect "standard output" with >

  ls myDir >/tmp/myDir.txt
  ls: myDir: No such file or directory
  

• To capture output including error messages, redirect "standard output" and "standard error" with &>

  ls myDir &>/tmp/myDir.txt
  

• To read responses from a file redirect "standard input" with <

pipelines

 ls|wc -l
 14

Directory Manipulation

• Make a new directory mkdir newDirectory
• Change current directory cd newDirectory
• Change back to last directory cd -
• What is my current directory pwd
• Current directory is . and parent directory is ..

Changing permissions

• 3 classes of user -- user (the owner), group, and other
• 3 basic permissions -- read (r), write (w) and execute (x)
• Programs/scripts MUST have the execute bit set in order to run
• chmod -- Change permissions of a file or directory

chmod u+x fileName     # Give owner execute permission
chmod g+w fileName     # Give group write permission
chmod go-rwx filename  # Remove permissions from all but owner

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