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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 |
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TABS(1P) POSIX Programmer's Manual TABS(1P)
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.
tabs — set terminal tabs
tabs [-n|-a|-a2|-c|-c2|-c3|-f|-p|-s|-u] [-T type]
tabs [-T type] n[[sep[+]n]...]
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.
The tabs utility shall conform to the Base Definitions volume of
POSIX.1‐2017, 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.
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.
Not used.
None.
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.1‐2017, 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.
Default.
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.
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
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.
None.
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.1‐2017 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.
None.
expand(1p), stty(1p), tput(1p), unexpand(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 TABS(1P)
Pages that refer to this page: expand(1p), tput(1p), unexpand(1p)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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