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Linux 2.6 - man page for tabs (linux section 1posix)

TABS(P) 			    POSIX Programmer's Manual				  TABS(P)

NAME
       tabs - set terminal tabs

SYNOPSIS
       tabs [ -n| -a| -a2| -c| -c2| -c3| -f| -p| -s| -u][+m[n]] [-T type]

       tabs [-T type][ +[n]] n1[,n2,...]

DESCRIPTION
       The  tabs utility shall display a series of characters that first clears the hardware ter-
       minal tab settings and then initializes the tab stops at the  specified	positions     and
       optionally adjusts the margin.

       The  phrase "tab-stop position N" shall be 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. The maximum number of tab stops allowed is terminal-depen-
       dent.

       It need not be possible to implement tabs on certain  terminals.   If  the  terminal  type
       obtained  from  the  TERM environment variable or -T option represents such a terminal, an
       appropriate diagnostic message shall be written to standard error and tabs shall exit with
       a status greater than zero.

OPTIONS
       The  tabs  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines,  except for various extensions: the options  -a2,
       -c2, and -c3 are multi-character.

       The following options shall be supported:

       -n     Specify  repetitive tab stops separated by a uniform number of column positions, n,
	      where n is a single-digit decimal number. The default usage of tabs with	no  argu-
	      ments  shall  be	equivalent  to	tabs-8.  When  -0 is used, the tab stops shall be
	      cleared and no new ones set.

       -a     1,10,16,36,72
	      Assembler, applicable to some mainframes.

       -a2    1,10,16,40,72
	      Assembler, applicable to some mainframes.

       -c     1,8,12,16,20,55
	      COBOL, normal format.

       -c2    1,6,10,14,49
	      COBOL, compact format (columns 1 to 6 omitted).

       -c3    1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
	      COBOL compact format (columns 1 to 6 omitted), with more tabs than -c2.

       -f     1,7,11,15,19,23
	      FORTRAN

       -p     1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
	      PL/1

       -s     1,10,55
	      SNOBOL

       -u     1,12,20,44
	      Assembler, applicable to some mainframes.

       -T  type
	      Indicate the type of terminal. If this option is not supplied and the TERM variable
	      is  unset  or null, an unspecified default terminal type shall be used. The setting
	      of type shall take precedence over the value in TERM .

OPERANDS
       The following operand shall be supported:

       n1[,n2,...]
	      A single command line argument that consists of  tab-stop  values  separated  using
	      either  commas  or  <blank>s. The application shall ensure that the tab-stop values
	      are positive decimal integers in strictly ascending order. If  any  number  (except
	      the  first one) is preceded by a plus sign, it is taken as an increment to be added
	      to the previous value. For example, the tab lists 1,10,20,30 and	1,10,+10,+10  are
	      considered to be identical.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of tabs:

       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, Inter-
	      nationalization 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  interna-
	      tionalization 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  argu-
	      ments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.

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

       TERM   Determine the terminal type. If this variable is unset  or  null,  and  if  the  -T
	      option is not specified, an unspecified default terminal type shall be used.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       If  standard output is a terminal, the appropriate sequence to clear and set the tab stops
       may be written to standard output in an unspecified format. If standard output  is  not	a
       terminal, undefined results occur.

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
       This utility makes use of the terminal's hardware tabs and the stty tabs option.

       This utility is not recommended for application use.

       Some integrated display units might not have escape sequences to set tab stops, but may be
       set by internal system calls. On  these	terminals,  tabs  works  if  standard  output  is
       directed to the terminal; if output is directed to another file, however, tabs fails.

EXAMPLES
       None.

RATIONALE
       Consideration  was  given to having the tput utility handle all of the functions described
       in tabs. However, the separate tabs utility was retained because it seems  more	intuitive
       to use a command named tabs than tput with a new option. The tput utility does not support
       setting or clearing tabs, and no known historical version of tabs supports the  capability
       of setting arbitrary tab stops.

       The   System   V   tabs	interface  is  very  complex;  the  version  in  this  volume  of
       IEEE Std 1003.1-2001 has a reduced feature list, but many of  the  features  omitted  were
       restored  as XSI extensions even though the supported languages and coding styles are pri-
       marily historical.

       There was considerable sentiment for specifying only a means of resetting the tabs back to
       a  known state-presumably the "standard" of tabs every eight positions. The following fea-
       tures were omitted:

	* Setting tab stops via the first line in a file, using -- file.  Since even the SVID has
	  no complete explanation of this feature, it is doubtful that it is in widespread use.

       In  an early proposal, a -t tablist option was added for consistency with expand; this was
       later removed when inconsistencies with the historical list of tabs were identified.

       Consideration was given to adding a -p option that would output the current  tab  settings
       so  that they could be saved and then later restored. This was not accepted because query-
       ing the tab stops of the terminal is not a capability in historical  terminfo  or  termcap
       facilities and might not be supported on a wide range of terminals.

FUTURE DIRECTIONS
       None.

SEE ALSO
       expand , stty , tput , unexpand

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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  TABS(P)


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