FAQ 4.34 How do I extract selected columns from a string?


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4.34: How do I extract selected columns from a string?

(contributed by brian d foy)

If you know the columns that contain the data, you can use "substr" to
extract a single column.

my $column = substr( $line, $start_column, $length );

You can use "split" if the columns are separated by whitespace or some
other delimiter, as long as whitespace or the delimiter cannot appear as
part of the data.

my $line = ' fred barney betty ';
my @columns = split /\s+/, $line;
# ( '', 'fred', 'barney', 'betty' );

my $line = 'fred||barney||betty';
my @columns = split /\|/, $line;
# ( 'fred', '', 'barney', '', 'betty' );

If you want to work with comma-separated values, don't do this since
that format is a bit more complicated. Use one of the modules that
handle that format, such as "Text::CSV", "Text::CSV_XS", or

If you want to break apart an entire line of fixed columns, you can use
"unpack" with the A (ASCII) format. By using a number after the format
specifier, you can denote the column width. See the "pack" and "unpack"
entries in perlfunc for more details.

my @fields = unpack( $line, "A8 A8 A8 A16 A4" );

Note that spaces in the format argument to "unpack" do not denote
literal spaces. If you have space separated data, you may want "split"


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