Originální popis anglicky:
tabs - set terminal tabs
Návod, kniha: POSIX Programmer's Manual
tabs [ -n| -a| -a2| -c| -c2| -c3| -f| -p|
-s| -u][+m[n]]
[ -T type]
tabs
[-T type][
+[n]]
n1
[,n2,...
]
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
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 .
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.
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
IEEE Std 1003.1-2001, 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 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 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 ,
stty ,
tput ,
unexpand
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 original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
