• grep

  • Use: searching for regular expressions in input data, printing lines that contain them. (If no files named, use stdin)

  • Syntax: grep [options] pattern [files]

  • Options:

    • -l -- print only filenames containing matches

    • -v -- print lines not matching pattern

    • -c -- print count of matching lines

    • -w -- match words

    • -i -- case-insensitivity

  • Pattern rules:

    • ^ -- beginning of line

    • $ -- end of line

    • . -- any single character

    • [ ... ] -- any character in ...

    • [^... ] -- any character not in ...

    • r* -- zero or more occurrences of r

  • Examples:

    $ who | grep pas $ grep -l varble *.[ch] $ vi `grep -l varble *.[ch]` $ grep -c tcsh$ /etc/passwd $ man lpr|grep -v '^[ \t]*$'|less

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• sort

  • Use: flexible sorting of input character/numeric data

  • Syntax: sort [options] [files]

  • Options:

    • -n -- sort numerically (default is ASCII)

    • -r -- sort in reverse order (default is ascending)

    • -d -- sort in dictionary order (case fold, ignore punctuation)

    • -b -- ignore leading blanks

    • -o file -- output to file

    • - -- sort stdin in addition to named files

    • +n -- skip n fields

    • -f -- fold upper to lower case

    • -tc -- fields separated by character c (default is whitespace)

  • Examples:

    $ du | sort -n $ ls -als|sort -n $ who | sort +3n +4n

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• awk

  • Usage: general-purpose manipulation and processing of input text/numeric data.

  • Simple use: each input line made up of fields; awk program specifies what to do with each line.

  • Examples:

    $ cat ~pas/emp.data $ awk ' $3 > 0 { print $1, $2 * $3 }' ~pas/emp.data $ awk ' $3 == 0 { print $1 }' ~pas/emp.data

  • In general, awk commands have the syntax:

    
        awk ' pattern { action } 
    	  pattern { action } 
              pattern { action }' file 
    

  • If file is unspecified, read from stdin.

  • END is a special pattern, matching end of input

  • awks has variables, initialized to zero

  • NR is a special variable, set to number of lines read.

    $ awk '{ sum += $3 } END { print "Average hours worked: " sum/NR }' ~pas/emp.data

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