CS 484 Home Page

CS 484 Week 3 topics

• Shell arguments and shell programming
  • $0 is the command
  • $1, $2, $3, ... are the command line argunments
  • $* is the command line arguments (a list of strings)
  • $@ is a string of the command line arguments
  • $# is the number of arguments
  • Example

    while [ $# -ne 0 ] ; do
    	echo $1
    	shift
    done
    

  • command exit status (0 means all OK, non-zero means failure)
  • test -- testing various conditions
    • conditions: -ne, -lt, -ge, etc
    • returns 0 while the condition holds
    • 'builtin'
    • [ ] notation (the command '[' is a synonym for 'test')
• using ls (more options than you care to know about)
  • -l: long listing
  • -t: time of last modification
  • -a: all files -- including files that start with '.'
  • -d: directory -- just list the name of a directory, not its contents

    ls -d /etc/rc?.d
    

  • -s: size -- list the size for each file
  • -C: columns -- list multiple file per line (even when the output is piped to another command)
  • -F: file type-- append a file type character to file names
  • -R: recursive -- list files in directories
• using find
  • cleaning up emacs droppings (building up commands to pass to sh):

    find . -name '*~' -print | sed 's/^/rm /' | sh
    

  • an alternate (building an argument list for the rm command):

    rm `find . -name '*~' -print`
    

  • yet another way, using the -exec action (you may prefer to use ok instead of exec):

    find . -name '*~' -exec rm '{}' ';'
    

  • other tests
    • -user, -group: owner/group of the file
    • -perm: permissions
    • -atime, -anewer: access time
    • -ctime, -cnewer: change (modification) time
    • -empty
    • -type
• locate and the update database
• regular expressions
• file globbing

Last Modified: February 15, 1999