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The GNU Awk User's Guide

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5.2 Examples of print Statements

Each print statement makes at least one line of output. However, it isn't limited to only one line. If an item value is a string that contains a newline, the newline is output along with the rest of the string. A single print statement can make any number of lines this way.

The following is an example of printing a string that contains embedded newlines (the `\n' is an escape sequence, used to represent the newline character; see section 3.2 Escape Sequences):

 
$ awk 'BEGIN { print "line one\nline two\nline three" }'
-| line one
-| line two
-| line three

The next example, which is run on the `inventory-shipped' file, prints the first two fields of each input record, with a space between them:

 
$ awk '{ print $1, $2 }' inventory-shipped
-| Jan 13
-| Feb 15
-| Mar 15
...

A common mistake in using the print statement is to omit the comma between two items. This often has the effect of making the items run together in the output, with no space. The reason for this is that juxtaposing two string expressions in awk means to concatenate them. Here is the same program, without the comma:

 
$ awk '{ print $1 $2 }' inventory-shipped
-| Jan13
-| Feb15
-| Mar15
...

To someone unfamiliar with the `inventory-shipped' file, neither example's output makes much sense. A heading line at the beginning would make it clearer. Let's add some headings to our table of months ($1) and green crates shipped ($2). We do this using the BEGIN pattern (see section The BEGIN and END Special Patterns) so that the headings are only printed once:

 
awk 'BEGIN {  print "Month Crates"
              print "----- ------" }
           {  print $1, $2 }' inventory-shipped

When run, the program prints the following:

 
Month Crates
----- ------
Jan 13
Feb 15
Mar 15
...

The only problem, however, is that the headings and the table data don't line up! We can fix this by printing some spaces between the two fields:

 
awk 'BEGIN { print "Month Crates"
             print "----- ------" }
           { print $1, "     ", $2 }' inventory-shipped

Lining up columns this way can get pretty complicated when there are many columns to fix. Counting spaces for two or three columns is simple, but any more than this can take up a lot of time. This is why the printf statement was created (see section Using printf Statements for Fancier Printing); one of its specialties is lining up columns of data.

Note: You can continue either a print or printf statement simply by putting a newline after any comma (see section awk Statements Versus Lines).


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