man/cat1p/unexpand.1p.txt
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unexpand(P) unexpand(P)
NAME unexpand - convert spaces to tabs SYNOPSIS unexpand [ -a| -t tablist][file...]<img src="../images/opt-end.gif" alt="[Option End]" bor- der="0"> DESCRIPTION The unexpand utility shall copy files or standard input to standard output, converting <blank>s at the beginning of each line into the maximum number of <tab>s followed by the minimum number of <space>s needed to fill the same column positions originally filled by the trans- lated <blank>s. By default, tabstops shall be set at every eighth column position. Each <backspace> shall be copied to the output, and shall cause the column posi- tion count for tab calculations to be decremented; the count shall never be decremented to a value less than one. OPTIONS The unexpand utility shall conform to the Base Defini- tions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines. The following options shall be supported: -a In addition to translating <blank>s at the begin- ning of each line, translate all sequences of two or more <blank>s immediately preceding a tab stop to the maximum number of <tab>s followed by the minimum number of <space>s needed to fill the same column positions originally filled by the translated <blank>s. -t tablist Specify the tab stops. The application shall ensure that the tablist option-argument is a sin- gle argument consisting of a single positive dec- imal integer or multiple positive decimal inte- gers, separated by <blank>s or commas, in ascend- ing order. If a single number is given, tabs shall be set tablist column positions apart instead of the default 8. If multiple numbers are given, the tabs shall be set at those specific column positions. The application shall ensure that each tab-stop position N is an integer value greater than zero, and the list shall be in strictly ascending order. This is taken to mean that, from the start of a line of output, tabbing to position N shall cause the next character output to be in the ( N+1)th column position on that line. When the -t option is not specified, the default shall be the equivalent of specifying -t 8 (except for the interac- tion with -a, described below). No <space>-to- <tab> conversions shall occur for charac- ters at positions beyond the last of those specified in a multiple tab-stop list. When -t is specified, the presence or absence of the -a option shall be ignored; conversion shall not be limited to the processing of leading <blank>s. OPERANDS The following operand shall be supported: file A pathname of a text file to be used as input. STDIN See the INPUT FILES section. INPUT FILES The input files shall be text files. ENVIRONMENT VARIABLES The following environment variables shall affect the execution of unexpand: LANG Provide a default value for the internationaliza- tion 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 cate- gories.) 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), the processing of <tab>s and <space>s, and for the determination of the width in column posi- tions each character would occupy on an output device. LC_MESSAGES Determine the locale that should be used to affect the format and contents of diagnostic mes- sages written to standard error. NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES . ASYNCHRONOUS EVENTS Default. STDOUT The standard output shall be equivalent to the input files with the specified <space>-to- <tab> conversions. 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 One non-intuitive aspect of unexpand is its restriction to leading spaces when neither -a nor -t is specified. Users who always want to convert all spaces in a file can easily alias unexpand to use the -a or -t 8 option. EXAMPLES None. RATIONALE On several occasions, consideration was given to adding a -t option to the unexpand utility to complement the -t in expand (see expand ). The historical intent of unex- pand was to translate multiple <blank>s into tab stops, where tab stops were a multiple of eight column posi- tions on most UNIX systems. An early proposal omitted -t because it seemed outside the scope of the User Porta- bility Utilities option; it was not described in any of the base documents. However, hard-coding tab stops every eight columns was not suitable for the interna- tional community and broke historical precedents for some vendors in the FORTRAN community, so -t was restored in conjunction with the list of valid extension categories considered by the standard developers. Thus, unexpand is now the logical converse of expand. FUTURE DIRECTIONS None. SEE ALSO expand , tabs COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operat- ing System Interface (POSIX), The Open Group Base Speci- fications Issue 6, Copyright (C) 2001-2003 by the Insti- tute 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.open- group.org/unix/online.html . POSIX 2003 unexpand(P) |