wc man page
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
wc — word, line, and byte or character count
wc [-c|-m] [-lw] [file...]
The wc utility shall read one or more input files and, by default, write the number of <newline> characters, words, and bytes contained in each input file to the standard output.
The utility also shall write a total count for all named files, if more than one input file is specified.
The wc utility shall consider a word to be a non-zero-length string of characters delimited by white space.
The wc utility shall conform to the Base Definitions volume of POSIX.1-2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
Write to the standard output the number of bytes in each input file.
Write to the standard output the number of <newline> characters in each input file.
Write to the standard output the number of characters in each input file.
Write to the standard output the number of words in each input file.
When any option is specified, wc shall report only the information requested by the specified options.
The following operand shall be supported:
A pathname of an input file. If no file operands are specified, the standard input shall be used.
The standard input shall be used if no file operands are specified, and shall be used if a file operand is '-' and the implementation treats the '-' as meaning standard input. Otherwise, the standard input shall not be used. See the Input Files section.
The input files may be of any type.
The following environment variables shall affect the execution of wc:
Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of POSIX.1-2008, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
If set to a non-empty string value, override the values of all the other internationalization variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files) and which characters are defined as white-space characters.
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and informative messages written to standard output.
Determine the location of message catalogs for the processing of LC_MESSAGES.
By default, the standard output shall contain an entry for each input file of the form:
"%d %d %d %s\n", <newlines>, <words>, <bytes>, <file>
If the -m option is specified, the number of characters shall replace the <bytes> field in this format.
If any options are specified and the -l option is not specified, the number of <newline> characters shall not be written.
If any options are specified and the -w option is not specified, the number of words shall not be written.
If any options are specified and neither -c nor -m is specified, the number of bytes or characters shall not be written.
If no input file operands are specified, no name shall be written and no <blank> characters preceding the pathname shall be written.
If more than one input file operand is specified, an additional line shall be written, of the same format as the other lines, except that the word total (in the POSIX locale) shall be written instead of a pathname and the total of each column shall be written as appropriate. Such an additional line, if any, is written at the end of the output.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
An error occurred.
Consequences of Errors
The following sections are informative.
The -m option is not a switch, but an option at the same level as -c. Thus, to produce the full default output with character counts instead of bytes, the command required is:
The output file format pseudo-printf() string differs from the System V version of wc:
which produces possibly ambiguous and unparsable results for very large files, as it assumes no number shall exceed six digits.
Some historical implementations use only <space>, <tab>, and <newline> as word separators. The equivalent of the ISO C standard isspace() function is more appropriate.
The -c option stands for “character” count, even though it counts bytes. This stems from the sometimes erroneous historical view that bytes and characters are the same size. Due to international requirements, the -m option (reminiscent of “multi-byte”) was added to obtain actual character counts.
Early proposals only specified the results when input files were text files. The current specification more closely matches historical practice. (Bytes, words, and <newline> characters are counted separately and the results are written when an end-of-file is detected.)
Historical implementations of the wc utility only accepted one argument to specify the options -c, -l, and -w. Some of them also had multiple occurrences of an option cause the corresponding count to be written multiple times and had the order of specification of the options affect the order of the fields on output, but did not document either of these. Because common usage either specifies no options or only one option, and because none of this was documented, the changes required by this volume of POSIX.1-2008 should not break many historical applications (and do not break any historical conforming applications).
The Base Definitions volume of POSIX.1-2008, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.unix.org/online.html .
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