wc: počet slov, řádků a bajtů nebo znaků

Originální popis anglicky: wc - word, line, and byte or character count

Návod, kniha: POSIX Programmer's Manual

STRUČNĚ

wc [-c|-m][-lw][file...]

POPIS / INSTRUKCE

The wc utility shall read one or more input files and, by default, write the number of <newline>s, 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.

OPTIONS

The wc utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following options shall be supported:

-c

Write to the standard output the number of bytes in each input file.

-l

Write to the standard output the number of <newline>s in each input file.

-m

Write to the standard output the number of characters in each input file.

-w

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.

OPERANDS

The following operand shall be supported:

file

A pathname of an input file. If no file operands are specified, the standard input shall be used.

 

STDIN

The standard input shall be used only if no file operands are specified. See the INPUT FILES section.

INPUT FILES

The input files may be of any type.

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of wc:

LANG

Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)

LC_ALL

If set to a non-empty string value, override the values of all the other internationalization variables.

LC_CTYPE

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.

LC_MESSAGES

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.

NLSPATH

Determine the location of message catalogs for the processing of LC_MESSAGES .

 

ASYNCHRONOUS EVENTS

Default.

STDOUT

By default, the standard output shall contain an entry for each input file of the form: 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>s 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>s 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.

STDERR

The standard error shall be used only for diagnostic messages.

OUTPUT FILES

None.

EXTENDED DESCRIPTION

None.

EXIT STATUS

The following exit values shall be returned:

 0

Successful completion.

>0

An error occurred.

 

CONSEQUENCES OF ERRORS

Default. The following sections are informative.

APPLICATION USAGE

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:

PŘÍKLADY POUŽITÍ

None.

RATIONALE

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>s 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 IEEE Std 1003.1-2001 should not break many historical applications (and do not break any historical conforming applications).

FUTURE DIRECTIONS

None.

SOUVISEJÍCÍ

cksum

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .