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TABS(1P)                   POSIX Programmer's Manual                  TABS(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

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 terminal 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 maxi-
       mum number of tab stops allowed is terminal-dependent.

       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 writ-
       ten 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 arguments 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, Internationalization Variables for  the  prece-
              dence 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  exam-
              ple, single-byte as opposed to multi-byte characters in arguments).

       LC_MESSAGES
              Determine  the locale that should be used to affect the format and contents of diagnostic messages writ-
              ten 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 sys-
       tem 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  lan-
       guages and coding styles are primarily historical.

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

        * Setting tab stops via the first line in a file, using -- file.  Since even the SVID has no complete explana-
          tion 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 querying 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  termi-
       nals.

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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                             TABS(1P)