chomp - Perldoc Browser (original) (raw)

This safer version of chop removes any trailing string that corresponds to the current value of $/ (also known as $INPUT_RECORD_SEPARATOR in the English module). It returns the total number of characters removed from all its arguments. It's often used to remove the newline from the end of an input record when you're worried that the final record may be missing its newline. When in paragraph mode ($/ = ''), it removes all trailing newlines from the string. When in slurp mode ($/ = undef) or fixed-length record mode ($/ is a reference to an integer or the like; see perlvar), chomp won't remove anything. If VARIABLE is omitted, it chomps $_. Example:

while (<>) {
    chomp;  # avoid \n on last field
    my @array = split(/:/);
    # ...
}

If VARIABLE is a hash, it chomps the hash's values, but not its keys, resetting the each iterator in the process.

You can actually chomp anything that's an lvalue, including an assignment:

chomp(my $cwd = `pwd`);
chomp(my $answer = <STDIN>);

If you chomp a list, each element is chomped, and the total number of characters removed is returned.

Note that parentheses are necessary when you're chomping anything that is not a simple variable. This is because chomp <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>w</mi><mi>d</mi><mo>=</mo><mi mathvariant="normal">‘</mi><mi>p</mi><mi>w</mi><mi>d</mi><mi mathvariant="normal">‘</mi><mo separator="true">;</mo><mi mathvariant="normal">‘</mi><mi mathvariant="normal">‘</mi><mi>i</mi><mi>s</mi><mi>i</mi><mi>n</mi><mi>t</mi><mi>e</mi><mi>r</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>t</mi><mi>e</mi><mi>d</mi><mi>a</mi><mi>s</mi><mi mathvariant="normal">‘</mi><mi mathvariant="normal">‘</mi><mo stretchy="false">(</mo><mi>c</mi><mi>h</mi><mi>o</mi><mi>m</mi><mi>p</mi></mrow><annotation encoding="application/x-tex">cwd = `pwd`; is interpreted as (chomp </annotation></semantics></math>cwd=‘pwd‘;‘‘isinterpretedas‘‘(chompcwd) = `pwd`;, rather than as chomp( <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>c</mi><mi>w</mi><mi>d</mi><mo>=</mo><mi mathvariant="normal">‘</mi><mi>p</mi><mi>w</mi><mi>d</mi><mi mathvariant="normal">‘</mi><mo stretchy="false">)</mo><mi mathvariant="normal">‘</mi><mi mathvariant="normal">‘</mi><mi>w</mi><mi>h</mi><mi>i</mi><mi>c</mi><mi>h</mi><mi>y</mi><mi>o</mi><mi>u</mi><mi>m</mi><mi>i</mi><mi>g</mi><mi>h</mi><mi>t</mi><mi>e</mi><mi>x</mi><mi>p</mi><mi>e</mi><mi>c</mi><mi>t</mi><mi mathvariant="normal">.</mi><mi>S</mi><mi>i</mi><mi>m</mi><mi>i</mi><mi>l</mi><mi>a</mi><mi>r</mi><mi>l</mi><mi>y</mi><mo separator="true">,</mo><mi mathvariant="normal">‘</mi><mi>c</mi><mi>h</mi><mi>o</mi><mi>m</mi><mi>p</mi></mrow><annotation encoding="application/x-tex">cwd = `pwd` ) which you might expect. Similarly, chomp </annotation></semantics></math>cwd=‘pwd‘)‘‘whichyoumightexpect.Similarly,‘chompx, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mi mathvariant="normal">‘</mi><mi>i</mi><mi>s</mi><mi>i</mi><mi>n</mi><mi>t</mi><mi>e</mi><mi>r</mi><mi>p</mi><mi>r</mi><mi>e</mi><mi>t</mi><mi>e</mi><mi>d</mi><mi>a</mi><mi>s</mi><mi mathvariant="normal">‘</mi><mi>c</mi><mi>h</mi><mi>o</mi><mi>m</mi><mi>p</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">y is interpreted as chomp(</annotation></semantics></math>y‘isinterpretedas‘chomp(x), <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>y</mi><mi mathvariant="normal">‘</mi><mi>r</mi><mi>a</mi><mi>t</mi><mi>h</mi><mi>e</mi><mi>r</mi><mi>t</mi><mi>h</mi><mi>a</mi><mi>n</mi><mi>a</mi><mi>s</mi><mi mathvariant="normal">‘</mi><mi>c</mi><mi>h</mi><mi>o</mi><mi>m</mi><mi>p</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">y rather than as chomp(</annotation></semantics></math>y‘ratherthanas‘chomp(x, $y).