PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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.

NAME         top

       tabs — set terminal tabs

SYNOPSIS         top

       tabs [n|−a|−a2|−c|−c2|−c3|−f|−p|−s|−u] [−T type]

       tabs [−T type] n[[sep[+]n]...]

DESCRIPTION         top

       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 maximum 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 written to standard error and tabs shall exit with a status
       greater than zero.

OPTIONS         top

       The tabs utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, 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         top

       The following operand shall be supported:

       n[[sep[+]n]...]
                 A single command line argument that consists of one or more
                 tab-stop values (n) separated by a separator character
                 (sep) which is either a <comma> or a <blank> character. The
                 application shall ensure that the tab-stop values are
                 positive decimal integers in strictly ascending order. If
                 any tab-stop value (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
                 "110+10+10" are considered to be identical.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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 POSIX.1‐2008, 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).

       LC_MESSAGES
                 Determine the locale that should be used to affect the
                 format and contents of diagnostic 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         top

       Default.

STDOUT         top

       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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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         top

       None.

RATIONALE         top

       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 POSIX.1‐2008 has a reduced feature list, but many of the
       features omitted were restored as part of the XSI option even though
       the supported languages and coding styles are primarily 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 features 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 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 terminals.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       expand(1p), stty(1p), tput(1p), unexpand(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            TABS(1P)