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File::Slurp(3)	      User Contributed Perl Documentation	File::Slurp(3)

NAME
       File::Slurp - Simple and Efficient Reading/Writing/Modifying of
       Complete Files

SYNOPSIS
	 use File::Slurp;

       # read in a whole file into a scalar
	 my $text = read_file( 'filename' ) ;

       # read in a whole file into an array of lines
	 my @lines = read_file( 'filename' ) ;

       # write out a whole file from a scalar
	 write_file( 'filename', $text ) ;

       # write out a whole file from an array of lines
	 write_file( 'filename', @lines ) ;

       # Here is a simple and fast way to load and save a simple config file #
       made of key=value lines.
	 my %conf = read_file( $file_name ) =~ /^(\w+)=(.*)$/mg ;
	 write_file( $file_name, {atomic => 1}, map "$_=$conf{$_}\n", keys
       %conf ) ;

       # insert text at the beginning of a file
	 prepend_file( 'filename', $text ) ;

       # in-place edit to replace all 'foo' with 'bar' in file
	 edit_file { s/foo/bar/g } 'filename' ;

       # in-place edit to delete all lines with 'foo' from file
	 edit_file_lines sub { $_ = '' if /foo/ }, 'filename' ;

       # read in a whole directory of file names (skipping . and ..)
	 my @files = read_dir( '/path/to/dir' ) ;

DESCRIPTION
       This module provides subs that allow you to read or write entire files
       with one simple call. They are designed to be simple to use, have
       flexible ways to pass in or get the file contents and to be very
       efficient.  There is also a sub to read in all the files in a directory
       other than "." and ".."

       These slurp/spew subs work for files, pipes and sockets, stdio, pseudo-
       files, and the DATA handle. Read more about why slurping files is a
       good thing in the file 'slurp_article.pod' in the extras/ directory.

       If you are interested in how fast these calls work, check out the
       slurp_bench.pl program in the extras/ directory. It compares many
       different forms of slurping. You can select the I/O direction, context
       and file sizes. Use the --help option to see how to run it.

   read_file
       This sub reads in an entire file and returns its contents to the
       caller.	In scalar context it returns the entire file as a single
       scalar. In list context it will return a list of lines (using the
       current value of $/ as the separator including support for paragraph
       mode when it is set to '').

	 my $text = read_file( 'filename' ) ;
	 my $bin = read_file( 'filename' { binmode => ':raw' } ) ;
	 my @lines = read_file( 'filename' ) ;
	 my $lines = read_file( 'filename', array_ref => 1 ) ;

       The first argument is the file to slurp in. If the next argument is a
       hash reference, then it is used as the options. Otherwise the rest of
       the argument list are is used as key/value options.

       If the file argument is a handle (if it is a ref and is an IO or GLOB
       object), then that handle is slurped in. This mode is supported so you
       slurp handles such as "DATA" and "STDIN". See the test handle.t for an
       example that does "open( '-|' )" and the child process spews data to
       the parant which slurps it in.  All of the options that control how the
       data is returned to the caller still work in this case.

       If the first argument is an overloaded object then its stringified
       value is used for the filename and that file is opened.	This is a new
       feature in 9999.14. See the stringify.t test for an example.

       By default "read_file" returns an undef in scalar contex or a single
       undef in list context if it encounters an error. Those are both
       impossible to get with a clean read_file call which means you can check
       the return value and always know if you had an error. You can change
       how errors are handled with the "err_mode" option.

       Speed Note: If you call read_file and just get a scalar return value it
       is now optimized to handle shorter files. This is only used if no
       options are used, the file is shorter then 100k bytes, the filename is
       a plain scalar and a scalar file is returned. If you want the fastest
       slurping, use the "buf_ref" or "scalar_ref" options (see below)

       NOTE: as of version 9999.06, read_file works correctly on the "DATA"
       handle. It used to need a sysseek workaround but that is now handled
       when needed by the module itself.

       You can optionally request that "slurp()" is exported to your code.
       This is an alias for read_file and is meant to be forward compatible
       with Perl 6 (which will have slurp() built-in).

       The options for "read_file" are:

       binmode

       If you set the binmode option, then its value is passed to a call to
       binmode on the opened handle. You can use this to set the file to be
       read in binary mode, utf8, etc. See perldoc -f binmode for more.

	       my $bin_data = read_file( $bin_file, binmode => ':raw' ) ;
	       my $utf_text = read_file( $bin_file, binmode => ':utf8' ) ;

       array_ref

       If this boolean option is set, the return value (only in scalar
       context) will be an array reference which contains the lines of the
       slurped file. The following two calls are equivalent:

	       my $lines_ref = read_file( $bin_file, array_ref => 1 ) ;
	       my $lines_ref = [ read_file( $bin_file ) ] ;

       chomp

       If this boolean option is set, the lines are chomped. This only happens
       if you are slurping in a list context or using the "array_ref" option.

       scalar_ref

       If this boolean option is set, the return value (only in scalar
       context) will be an scalar reference to a string which is the contents
       of the slurped file. This will usually be faster than returning the
       plain scalar. It will also save memory as it will not make a copy of
       the file to return. Run the extras/slurp_bench.pl script to see speed
       comparisons.

	       my $text_ref = read_file( $bin_file, scalar_ref => 1 ) ;

       buf_ref

       You can use this option to pass in a scalar reference and the slurped
       file contents will be stored in the scalar. This can be used in
       conjunction with any of the other options. This saves an extra copy of
       the slurped file and can lower ram usage vs returning the file. It is
       usually the fastest way to read a file into a scalar. Run the
       extras/slurp_bench.pl script to see speed comparisons.

	       read_file( $bin_file, buf_ref => \$buffer ) ;

       blk_size

       You can use this option to set the block size used when slurping from
       an already open handle (like \*STDIN). It defaults to 1MB.

	       my $text_ref = read_file( $bin_file, blk_size => 10_000_000,
						    array_ref => 1 ) ;

       err_mode

       You can use this option to control how read_file behaves when an error
       occurs. This option defaults to 'croak'. You can set it to 'carp' or to
       'quiet to have no special error handling. This code wants to carp and
       then read another file if it fails.

	       my $text_ref = read_file( $file, err_mode => 'carp' ) ;
	       unless ( $text_ref ) {

		       # read a different file but croak if not found
		       $text_ref = read_file( $another_file ) ;
	       }

	       # process ${$text_ref}

   write_file
       This sub writes out an entire file in one call.

	 write_file( 'filename', @data ) ;

       The first argument to "write_file" is the filename. The next argument
       is an optional hash reference and it contains key/values that can
       modify the behavior of "write_file". The rest of the argument list is
       the data to be written to the file.

	 write_file( 'filename', {append => 1 }, @data ) ;
	 write_file( 'filename', {binmode => ':raw'}, $buffer ) ;

       As a shortcut if the first data argument is a scalar or array
       reference, it is used as the only data to be written to the file. Any
       following arguments in @_ are ignored. This is a faster way to pass in
       the output to be written to the file and is equivalent to the "buf_ref"
       option of "read_file". These following pairs are equivalent but the
       pass by reference call will be faster in most cases (especially with
       larger files).

	 write_file( 'filename', \$buffer ) ;
	 write_file( 'filename', $buffer ) ;

	 write_file( 'filename', \@lines ) ;
	 write_file( 'filename', @lines ) ;

       If the first argument is a handle (if it is a ref and is an IO or GLOB
       object), then that handle is written to. This mode is supported so you
       spew to handles such as \*STDOUT. See the test handle.t for an example
       that does "open( '-|' )" and child process spews data to the parent
       which slurps it in.  All of the options that control how the data are
       passed into "write_file" still work in this case.

       If the first argument is an overloaded object then its stringified
       value is used for the filename and that file is opened.	This is new
       feature in 9999.14. See the stringify.t test for an example.

       By default "write_file" returns 1 upon successfully writing the file or
       undef if it encountered an error. You can change how errors are handled
       with the "err_mode" option.

       The options are:

       binmode

       If you set the binmode option, then its value is passed to a call to
       binmode on the opened handle. You can use this to set the file to be
       read in binary mode, utf8, etc. See perldoc -f binmode for more.

	       write_file( $bin_file, {binmode => ':raw'}, @data ) ;
	       write_file( $bin_file, {binmode => ':utf8'}, $utf_text ) ;

       perms

       The perms option sets the permissions of newly-created files. This
       value is modified by your process's umask and defaults to 0666 (same as
       sysopen).

       NOTE: this option is new as of File::Slurp version 9999.14;

       buf_ref

       You can use this option to pass in a scalar reference which has the
       data to be written. If this is set then any data arguments (including
       the scalar reference shortcut) in @_ will be ignored. These are
       equivalent:

	       write_file( $bin_file, { buf_ref => \$buffer } ) ;
	       write_file( $bin_file, \$buffer ) ;
	       write_file( $bin_file, $buffer ) ;

       atomic

       If you set this boolean option, the file will be written to in an
       atomic fashion. A temporary file name is created by appending the pid
       ($$) to the file name argument and that file is spewed to. After the
       file is closed it is renamed to the original file name (and rename is
       an atomic operation on most OS's). If the program using this were to
       crash in the middle of this, then the file with the pid suffix could be
       left behind.

       append

       If you set this boolean option, the data will be written at the end of
       the current file. Internally this sets the sysopen mode flag O_APPEND.

	       write_file( $file, {append => 1}, @data ) ;

	You
       can import append_file and it does the same thing.

       no_clobber

       If you set this boolean option, an existing file will not be
       overwritten.

	       write_file( $file, {no_clobber => 1}, @data ) ;

       err_mode

       You can use this option to control how "write_file" behaves when an
       error occurs. This option defaults to 'croak'. You can set it to 'carp'
       or to 'quiet' to have no error handling other than the return value. If
       the first call to "write_file" fails it will carp and then write to
       another file. If the second call to "write_file" fails, it will croak.

	       unless ( write_file( $file, { err_mode => 'carp', \$data ) ;

		       # write a different file but croak if not found
		       write_file( $other_file, \$data ) ;
	       }

   overwrite_file
       This sub is just a typeglob alias to write_file since write_file always
       overwrites an existing file. This sub is supported for backwards
       compatibility with the original version of this module. See write_file
       for its API and behavior.

   append_file
       This sub will write its data to the end of the file. It is a wrapper
       around write_file and it has the same API so see that for the full
       documentation. These calls are equivalent:

	       append_file( $file, @data ) ;
	       write_file( $file, {append => 1}, @data ) ;

   prepend_file
       This sub writes data to the beginning of a file. The previously
       existing data is written after that so the effect is prepending data in
       front of a file. It is a counterpart to the append_file sub in this
       module. It works by first using "read_file" to slurp in the file and
       then calling "write_file" with the new data and the existing file data.

       The first argument to "prepend_file" is the filename. The next argument
       is an optional hash reference and it contains key/values that can
       modify the behavior of "prepend_file". The rest of the argument list is
       the data to be written to the file and that is passed to "write_file"
       as is (see that for allowed data).

       Only the "binmode" and "err_mode" options are supported. The
       "write_file" call has the "atomic" option set so you will always have a
       consistant file. See above for more about those options.

       "prepend_file" is not exported by default, you need to import it
       explicitly.

	       use File::Slurp qw( prepend_file ) ;
	       prepend_file( $file, $header ) ;
	       prepend_file( $file, \@lines ) ;
	       prepend_file( $file, { binmode => 'raw:'}, $bin_data ) ;

   edit_file, edit_file_lines
       These subs read in a file into $_, execute a code block which should
       modify $_ and then write $_ back to the file. The difference between
       them is that "edit_file" reads the whole file into $_ and calls the
       code block one time. With "edit_file_lines" each line is read into $_
       and the code is called for each line. In both cases the code should
       modify $_ if desired and it will be written back out. These subs are
       the equivalent of the -pi command line options of Perl but you can call
       them from inside your program and not fork out a process. They are in
       @EXPORT_OK so you need to request them to be imported on the use line
       or you can import both of them with:

	       use File::Slurp qw( :edit ) ;

       The first argument to "edit_file" and "edit_file_lines" is a code block
       or a code reference. The code block is not followed by a comma (as with
       grep and map) but a code reference is followed by a comma. See the
       examples below for both styles. The next argument is the filename. The
       last argument is an optional hash reference and it contains key/values
       that can modify the behavior of "prepend_file".

       Only the "binmode" and "err_mode" options are supported. The
       "write_file" call has the "atomic" option set so you will always have a
       consistant file. See above for more about those options.

       Each group of calls below show a Perl command line instance and the
       equivalent calls to "edit_file" and "edit_file_lines".

	       perl -0777 -pi -e 's/foo/bar/g' filename
	       use File::Slurp qw( edit_file ) ;
	       edit_file { s/foo/bar/g } 'filename' ;
	       edit_file sub { s/foo/bar/g }, 'filename' ;
	       edit_file \&replace_foo, 'filename' ;
	       sub replace_foo { s/foo/bar/g }

	       perl -pi -e '$_ = "" if /foo/' filename
	       use File::Slurp qw( edit_file_lines ) ;
	       use File::Slurp ;
	       edit_file_lines { $_ = '' if /foo/ } 'filename' ;
	       edit_file_lines sub { $_ = '' if /foo/ }, 'filename' ;
	       edit_file \&delete_foo, 'filename' ;
	       sub delete_foo { $_ = '' if /foo/ }

   read_dir
       This sub reads all the file names from directory and returns them to
       the caller but "." and ".." are removed by default.

	       my @files = read_dir( '/path/to/dir' ) ;

       The first argument is the path to the directory to read.	 If the next
       argument is a hash reference, then it is used as the options.
       Otherwise the rest of the argument list are is used as key/value
       options.

       In list context "read_dir" returns a list of the entries in the
       directory. In a scalar context it returns an array reference which has
       the entries.

       err_mode

       If the "err_mode" option is set, it selects how errors are handled (see
       "err_mode" in "read_file" or "write_file").

       keep_dot_dot

       If this boolean option is set, "." and ".." are not removed from the
       list of files.

	       my @all_files = read_dir( '/path/to/dir', keep_dot_dot => 1 ) ;

       prefix

       If this boolean option is set, the string "$dir/" is prefixed to each
       dir entry. This means you can directly use the results to open files. A
       common newbie mistake is not putting the directory in front of entries
       when opening themn.

	       my @paths = read_dir( '/path/to/dir', prefix => 1 ) ;

   EXPORT
	 These are exported by default or with
	       use File::Slurp qw( :std ) ;

	 read_file write_file overwrite_file append_file read_dir

	 These are exported with
	       use File::Slurp qw( :edit ) ;

	 edit_file edit_file_lines

	 You can get all subs in the module exported with
	       use File::Slurp qw( :all ) ;

   LICENSE
	 Same as Perl.

   SEE ALSO
       An article on file slurping in extras/slurp_article.pod. There is also
       a benchmarking script in extras/slurp_bench.pl.

   BUGS
       If run under Perl 5.004, slurping from the DATA handle will fail as
       that requires B.pm which didn't get into core until 5.005.

AUTHOR
       Uri Guttman, <uri AT stemsystems DOT com>

perl v5.18.1			  2011-05-30			File::Slurp(3)
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