=pod =encoding UTF-8 =head1 NAME File::ByLine - Line-by-line file access loops =head1 VERSION version 1.192590 =head1 SYNOPSIS use File::ByLine; # # Procedural Interface (Simple!) # # Execute a routine for each line of a file dolines { say "Line: $_" } "file.txt"; forlines "file.txt", sub { say "Line: $_" }; # Grep (match) lines of a file my (@result) = greplines { m/foo/ } "file.txt"; # Apply a function to each line and return result my (@result) = maplines { lc($_) } "file.txt"; # Parallelized forlines/dolines routines # (Note: Requires Parallel::WorkUnit to be installed) parallel_dolines { foo($_) } "file.txt", 10; parallel_forlines "file.txt", 10, sub { foo($_); }; # Parallelized maplines and greplines my (@result) = parallel_greplines { m/foo/ } "file.txt", 10; my (@result) = parallel_maplines { lc($_) } "file.txt", 10; # Read an entire file, split into lines my (@result) = readlines "file.txt"; # Write out a file writefile "file.txt", @lines; # Since version 2.182360 # Append to a file appendfile "file.txt", @lines; # Since version 2.182362 # # Object Oriented Interface (More Powerful!) # # Execute a routine for each line of a file my $byline = File::ByLine->new(); $byline->do( sub { say "Line: $_" }, "file.txt"); # Grep (match) lines of a file my $byline = File::ByLine->new(); my (@result) = $byline->grep( sub { m/foo/ }, "file.txt"); # Apply a function to each line and return result my $byline = File::ByLine->new(); my (@result) = $byline->map( sub { lc($_) }, "file.txt"); # Parallelized routines # (Note: Requires Parallel::WorkUnit to be installed) my $byline = File::ByLine->new(); $byline->processes(10); $byline->do( sub { foo($_) }, "file.txt"); my (@grep_result) = $byline->grep( sub { m/foo/ }, "file.txt"); my (@map_result) = $byline->map( sub { lc($_) }, "file.txt"); # Skip the header line my $byline = File::ByLine->new(); $byline->header_skip(1); $byline->do( sub { foo($_) }, "file.txt"); my (@grep_result) = $byline->grep( sub { m/foo/ }, "file.txt"); my (@map_result) = $byline->map( sub { lc($_) }, "file.txt"); # Process the header line my $byline = File::ByLine->new(); $byline->header_handler( sub { say $_; } ); $byline->do( sub { foo($_) }, "file.txt"); my (@grep_result) = $byline->grep( sub { m/foo/ }, "file.txt"); my (@map_result) = $byline->map( sub { lc($_) }, "file.txt"); # Read an entire file, split into lines my (@result) = $byline->lines("file.txt"); # Alternative way of specifying filenames my $byline = File::ByLine->new(); $byline->file("file.txt") $byline->do( sub { foo($_) } ); my (@grep_result) = $byline->grep( sub { m/foo/ } ); my (@map_result) = $byline->map( sub { lc($_) } ); =head1 DESCRIPTION Finding myself writing the same trivial loops to read files, or relying on modules like C that didn't quite do what I needed (abstracting the loop), it was clear something easy, simple, and sufficiently Perl-ish was needed. =head1 FUNCTIONS =head2 dolines dolines { say "Line: $_" } "file.txt"; dolines \&func, "file.txt"; This function calls a coderef once for each line in the file. The file is read line-by-line, removes the newline character(s), and then executes the coderef. Each line (without newline) is passed to the coderef as the only parameter to the coderef. It is also placed into C<$_>. This function returns the number of lines in the file. This is similar to C, except for order of arguments. The author recommends this form for short code blocks - I.E. a coderef that fits on one line. For longer, multi-line code blocks, the author recommends the C syntax. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head2 forlines forlines "file.txt", sub { say "Line: $_" }; forlines "file.txt", \&func; This function calls a coderef once for each line in the file. The file is read line-by-line, removes the newline character(s), and then executes the coderef. Each line (without newline) is passed to the coderef as the only parameter to the coderef. It is also placed into C<$_>. This function returns the number of lines in the file. This is similar to C, except for order of arguments. The author recommends this when using longer, multi-line code blocks, even though it is not orthogonal with the C/C routines. =head2 parallel_dolines my (@result) = parallel_dolines { foo($_) } "file.txt", 10; Requires L to be installed. Three parameters are required: a codref, a filename, and number of simultaneous child threads to use. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. This function performs similar to C, except that it does its' operations in parallel using C and L. Because the code in the coderef is executed in a child process, any changes it makes to variables in high scopes will not be visible outside that single child. In general, it will be safest to not modify anything that belongs outside this scope. Note that the file will be read in several chunks, with each chunk being processed in a different thread. This means that the child threads may be operating on very different sections of the file simultaneously and no specific order of execution of the coderef should be expected! Because of the mechanism used to split the file into chunks for processing, each thread may process a somewhat different number of lines. This is particularly true if there are a mix of very long and very short lines. The splitting routine splits the file into roughly equal size chunks by byte count, not line count. Otherwise, this function is identical to C. See the documentation for C or C for information about how this might differ from C. =head2 parallel_forlines my (@result) = parallel_forlines "file.txt", 10, sub { foo($_) }; Requires L to be installed. Three parameters are required: a filename, a codref, and number of simultaneous child threads to use. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. This function performs similar to C, except that it does its' operations in parallel using C and L. Because the code in the coderef is executed in a child process, any changes it makes to variables in high scopes will not be visible outside that single child. In general, it will be safest to not modify anything that belongs outside this scope. Note that the file will be read in several chunks, with each chunk being processed in a different thread. This means that the child threads may be operating on very different sections of the file simultaneously and no specific order of execution of the coderef should be expected! Because of the mechanism used to split the file into chunks for processing, each thread may process a somewhat different number of lines. This is particularly true if there are a mix of very long and very short lines. The splitting routine splits the file into roughly equal size chunks by byte count, not line count. Otherwise, this function is identical to C. See the documentation for C or C for information about how this might differ from C. =head2 greplines my (@result) = greplines { m/foo/ } "file.txt"; Requires L to be installed. This function calls a coderef once for each line in the file, and, based on the return value of that coderef, returns only the lines where the coderef evaluates to true. This is similar to the C built-in function, except operating on file input rather than array input. Each line (without newline) is passed to the coderef as the only parameter to the coderef. It is also placed into C<$_>. This function returns the lines for which the coderef evaluates as true. =head2 parallel_greplines my (@result) = parallel_greplines { m/foo/ } "file.txt", 10; Three parameters are required: a coderef, filename, and number of simultaneous child threads to use. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. This function performs similar to C, except that it does its' operations in parallel using C and L. Because the code in the coderef is executed in a child process, any changes it makes to variables in high scopes will not be visible outside that single child. In general, it will be safest to not modify anything that belongs outside this scope. If a large amount of data is returned, the overhead of passing the data from child to parents may exceed the benefit of parallelization. However, if there is substantial line-by-line processing, there likely will be a speedup, but trivial loops will not speed up. Note that the file will be read in several chunks, with each chunk being processed in a different thread. This means that the child threads may be operating on very different sections of the file simultaneously and no specific order of execution of the coderef should be expected! However, the results will be returned in the same order as C would return them. Because of the mechanism used to split the file into chunks for processing, each thread may process a somewhat different number of lines. This is particularly true if there are a mix of very long and very short lines. The splitting routine splits the file into roughly equal size chunks by byte count, not line count. Otherwise, this function is identical to C. =head2 maplines my (@result) = maplines { lc($_) } "file.txt"; This function calls a coderef once for each line in the file, and, returns an array of return values from those calls. This follows normal Perl rules - basically if the coderef returns a list, all elements of that list are added as distinct elements to the return value array. If the coderef returns an empty list, no elements are added. Each line (without newline) is passed to the coderef as the only parameter to the coderef. It is also placed into C<$_>. This is meant to be similar to the built-in C function. Because of the mechanism used to split the file into chunks for processing, each thread may process a somewhat different number of lines. This is particularly true if there are a mix of very long and very short lines. The splitting routine splits the file into roughly equal size chunks by byte count, not line count. This function returns the lines for which the coderef evaluates as true. =head2 parallel_maplines my (@result) = parallel_maplines { lc($_) } "file.txt", 10; Three parameters are required: a coderef, filename, and number of simultaneous child threads to use. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. This function performs similar to C, except that it does its' operations in parallel using C and L. Because the code in the coderef is executed in a child process, any changes it makes to variables in high scopes will not be visible outside that single child. In general, it will be safest to not modify anything that belongs outside this scope. If a large amount of data is returned, the overhead of passing the data from child to parents may exceed the benefit of parallelization. However, if there is substantial line-by-line processing, there likely will be a speedup, but trivial loops will not speed up. Note that the file will be read in several chunks, with each chunk being processed in a different thread. This means that the child threads may be operating on very different sections of the file simultaneously and no specific order of execution of the coderef should be expected! However, the results will be returned in the same order as C would return them. Otherwise, this function is identical to C. =head2 readlines my (@result) = readlines "file.txt"; This function simply returns an array of lines (without newlines) read from a file. =head2 writefile writefile "file.txt", @lines; This was added in version 2.181850. This function creates a file (overwriting existing files) and writes each line to the file. Each line (array element) is terminated with a newline, except the last line IF the last line ends in a newline itself. I.E. the following will write a file with three lines, each terminated by a newline: writefile "file.txt", "a", "b", "c"; So will this: writefile "file.txt", "a\nb", "c\n"; There is no object-oriented equivilent to this function. This does not return any value. =head2 appendfile appendfile "file.txt", @lines; This was added in version 2.181862. This function creates or appends to a file (appending on existing files) and writes each line to the end of the file. Each line (array element) is terminated with a newline, except the last line IF the last line ends in a newline itself. I.E. the following will append to a file with three lines, each terminated by a newline: appendfile "file.txt", "a", "b", "c"; So will this: appendfile "file.txt", "a\nb", "c\n"; There is no object-oriented equivilent to this function. This does not return any value. =head1 OBJECT ORIENTED INTERFACE The object oriented interface was implemented in version 1.181860. =head2 new my $byline = File::ByLine->new(); Constructs a new object, suitable for the object oriented calls below. =head2 ATTRIBUTES =head3 extended_info $extended = $byline->extended_info(); $byline->extended_info(1); This was added in version 1.181951. Gets and sets the "extended information" flag. This defaults to false, but if set to a true value this will pass a second parameter to all user-defined code (such as the per-line code function in C and C and the C function. For all code, this information will be passed as the second argument to the user defined code. It will be a hashref with the following keys defined: =over 4 =item C - The filename currently being processed =item C - An object corresponding to either the current explicit or implicit C object =item C - Which child process (first process is zero) =back This object should not be modified by user code. In addition, no attributes of the explict or implicit File::ByLine object passed as part of this hashref should be modified within user code. =head3 file my $file = $byline->file(); $byline->file("abc.txt"); $byline->file( [ "abc.txt", "def.txt" ] ); $byline->file( "$abc.txt", "def.txt" ); Gets and sets the default filename used by the methods in the object oriented interface. The default value is C which indicates that no default filename is provided. Instead of a single filename, a list or arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head3 header_all_files my $all_files = $byline->header_all_files(); $byline->header_all_files(1); Gets and sets whether the object oriented methods will call C for every file if multiple files are passed into the C attribute. The anticipated usage of this would be with C set to true, with the C function examining the C attribute of the extended info hashref. Note that all headers may be read before any line in any file is read, to better accommodate parallel code execution. I.E. the headers of all files may be read at once before any data line is read. =head3 header_handler my $handler = $byline->header_handler(); $byline->header_handler( sub { ... } ); Specifies code that should be executed on the header row of the input file. This defaults to C, which indicates no header handler is specified. When a header handler is specified, the first row of the file is sent to this handler, and is not sent to the code provided to the various do/grep/map/lines methods in the object oriented interface. The code is called with one or two parameters, the header line, and, if the C attribute is set, the extended information hashref. The header line is also stored in C<$_>. When set, this is always executed in the parent process, not in the child processes that are spawned (in the case of C being greater than one). You cannot set this to true while a C value is set. =head3 processes my $procs = $byline->processes(); $byline->processes(10); This gets and sets the degree of parallelism most methods will use. The default degree is C<1>, which indicates all tasks should only use a single process. Specifying C<2> or greater will use multiple processes to operate on the file (see documentation for the parallel_* functions described above for more details). =head3 skip_unreadable my $unreadable = $byline->skip_unreadable(); $byline->skip_unreadable(10); This was added in version 1.181980. If this attribute is true, unreadable files are treated as empty files during processing. The default is false, in which case an exception is thrown when an access attempt is made to an unreadable file. =head3 Short Name Aliases for Attributes $byline->f(); # Alias for file $byline->ei(); # Alias for extended_info $byline->haf(); # Alias for header_all_files $byline->hh(); # Alias for header_handler $byline->hs(); # Alias for header_skip $byline->p(); # Alias for processes $byline->su(); # Alias for skip_unreadable Short name aliases were added in version 1.181980. Each attribute listed above has a corresponding short name. This short name can also be used as a constructor argument. =head2 METHODS =head3 do $byline->do( sub { ... }, "file.txt" ); This performs the C functionality, calling the code provided. If the filename is not provided, the C attribute is used for this. See the C and C functions for more information on how this functions. Each line (without newline) is passed to the coderef as the first parameter to the coderef. It is also placed into C<$_>. If the C attribute is true, the extended information hashref will be passed as the second parameter. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head3 grep my (@output) = $byline->grep( sub { ... }, "file.txt" ); This performs the C functionality, calling the code provided. If the filename is not provided, the C attribute is used for this. See the C and C functions for more information on how this functions. Each line (without newline) is passed to the coderef as the first parameter to the coderef. It is also placed into C<$_>. If the C attribute is true, the extended information hashref will be passed as the second parameter. The output is a list of all input lines where the code reference produces a true result. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head3 map my (@output) = $byline->map( sub { ... }, "file.txt" ); This performs the C functionality, calling the code provided. If the filename is not provided, the C attribute is used for this. See the C and C functions for more information on how this functions. Each line (without newline) is passed to the coderef as the first parameter to the coderef. It is also placed into C<$_>. If the C attribute is true, the extended information hashref will be passed as the second parameter. The output is the list produced by calling the passed-in code repeatively for each line of input. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head3 lines my (@output) = $byline->lines( "file.txt" ); This performs the C functionality. If the filename is not provided, the C attribute is used for this. See the C function for more information on how this functions. The output is a list of all input lines. Note that this function is unaffected by the value of the C attribute - it always executes in the parent process. Instead of a single filename, an arrayref can be passed in, in which case the files are read in turn as if they are all one file. Note that if the file doesn't end in a newline, a newline is inserted before processing the next file. =head1 SUGGESTED DEPENDENCY The L module is a recommended dependency. It is required to use the C functions - all other functionality works fine without it. Some CPAN clients will automatically try to install recommended dependency, but others won't (L often, but not always, will; L will not by default). In the cases where it is not automatically installed, you need to install L to get this functionality. =head1 EXPRESSING APPRECIATION If this module makes your life easier, or helps make you (or your workplace) a ton of money, I always enjoy hearing about it! My response when I hear that someone uses my module is to go back to that module and spend a little time on it if I think there's something to improve - it's motivating when you hear someone appreciates your work! I don't seek any money for this - I do this work because I enjoy it. That said, should you want to show appreciation financially, few things would make me smile more than knowing that you sent a donation to a Gender-related charity. =head1 AUTHOR Joelle Maslak =head1 COPYRIGHT AND LICENSE This software is copyright (c) 2018 by Joelle Maslak. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. =cut