UNIX Shells by Example (4th Edition)

6.9. awk Commands in a Script File

When you have multiple awk pattern/action statements, it is often much easier to put the statements in a script. The script is a file containing awk comments and statements. If statements and actions are on the same line, they are separated by semicolons. If statements are on separate lines, semicolons are not necessary. If an action follows a pattern, the opening curly brace must be on the same line as the pattern. Comments are preceded by a pound ( # ) sign.

Example 6.29.

% cat employees Tom Jones:4424:5/12/66:54335 Mary Adams:5346:11/4/63:28765 Billy Black:1683:9/23/44:336500 Sally Chang:1654:7/22/54:65000 Jose Tomas:1683:9/23/44:33650 (The Awk Script) % cat info 1 # My first awk script by Jack Sprat # Script name: info; Date: February 28, 2004 2 /Tom/{print "Tom's birthday is "} 3 /Mary/{print NR,

% cat employees Tom Jones:4424:5/12/66:54335 Mary Adams:5346:11/4/63:28765 Billy Black:1683:9/23/44:336500 Sally Chang:1654:7/22/54:65000 Jose Tomas:1683:9/23/44:33650 (The Awk Script) % cat info 1 # My first awk script by Jack Sprat # Script name : info; Date: February 28, 2004 2 /Tom/{print "Tom's birthday is "$3} 3 /Mary/{print NR, $0} 4 /^Sally/{print "Hi Sally. " $1 " has a salary of $" $4 "."} # End of info script (The Command Line) 5 % nawk “F: “f info employees2 Tom's birthday is 5/12/66 2 Mary Adams:5346:11/4/63:28765 Hi Sally. Sally Chang has a salary of $65000. } 4 /^Sally/{print "Hi Sally. " " has a salary of $" "."} # End of info script (The Command Line) 5 % nawk F: f info employees2 Tom's birthday is 5/12/66 2 Mary Adams:5346:11/4/63:28765 Hi Sally. Sally Chang has a salary of 000.

EXPLANATION

1. These are comment lines.

2. If the regular expression Tom is matched against an input line, the string Tom's birthday is and the value of the third field ( $3 ) are printed.

3. If the regular expression Mary is matched against an input line, the action block prints NR , the number of the current record, and the record.

4. If the regular expression Sally is found at the beginning of the input line, the string Hi Sally . is printed, followed by the value of the first field ( $1 ), the string has a salary of $ , and the value of the fourth field ( $4 ).

5. The nawk command is followed by the “F: option, specifying the colon to be the field separator. The “f option is followed by the name of the awk script. Awk will read instructions from the info file. The input file, employees2 , is next .