- The tabs program clears and sets tab-stops on the terminal. This uses
- the terminfo clear_all_tabs and set_tab capabilities. If either is
- absent, tabs is unable to clear/set tab-stops. The terminal should be
+ The tabs program clears and sets tab-stops on the terminal. This uses
+ the terminfo clear_all_tabs and set_tab capabilities. If either is
+ absent, tabs is unable to clear/set tab-stops. The terminal should be
configured to use hard tabs, e.g.,
stty tab0
- Like clear(1), tabs writes to the standard output. You can redirect
- the standard output to a file (which prevents tabs from actually
- changing the tabstops), and later cat the file to the screen, setting
+ Like clear(1), tabs writes to the standard output. You can redirect
+ the standard output to a file (which prevents tabs from actually
+ changing the tabstops), and later cat the file to the screen, setting
tabstops at that point.
These are hardware tabs, which cannot be queried rapidly by
@@ -77,42 +77,42 @@
tabs -8
- or use the reset program, since the normal initialization sequences do
+ or use the reset program, since the normal initialization sequences do
not ensure that tab-stops are reset.
- -Tname
- Tell tabs which terminal type to use. If this option is not
- given, tabs will use the $TERM environment variable. If that is
- not set, it will use the ansi+tabs entry.
+ -Tname
+ Tell tabs which terminal type to use. If this option is not
+ given, tabs will use the $TERM environment variable. If that is
+ not set, it will use the ansi+tabs entry.
- -d The debugging option shows a ruler line, followed by two data
+ -d The debugging option shows a ruler line, followed by two data
lines. The first data line shows the expected tab-stops marked
with asterisks. The second data line shows the actual tab-stops,
marked with asterisks.
- -n This option tells tabs to check the options and run any debugging
+ -n This option tells tabs to check the options and run any debugging
option, but not to modify the terminal settings.
- -V reports the version of ncurses which was used in this program, and
+ -V reports the version of ncurses which was used in this program, and
exits.
- The tabs program processes a single list of tab stops. The last option
+ The tabs program processes a single list of tab stops. The last option
to be processed which defines a list is the one that determines the
list to be processed.
- Use a single number as an option, e.g., "-5" to set tabs at the given
+ Use a single number as an option, e.g., "-5" to set tabs at the given
interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
to the right margin of the screen.
- Use "-0" to clear all tabs.
+ Use "-0" to clear all tabs.
- Use "-8" to set tabs to the standard interval.
+ Use "-8" to set tabs to the standard interval.
- X/Open defines several predefined lists of tab stops.
+ POSIX defines several predefined lists of tab stops.
+
+ -a Assembler, IBM S/370, first format
+ 1,10,16,36,72
+
+ -a2 Assembler, IBM S/370, second format
+ 1,10,16,40,72
+
+ -c COBOL, normal format
+ 1,8,12,16,20,55
+
+ -c2 COBOL compact format
+ 1,6,10,14,49
- -a Assembler, IBM S/370, first format
+ -c3 COBOL compact format extended
+ 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
- -a2 Assembler, IBM S/370, second format
+ -f FORTRAN
+ 1,7,11,15,19,23
- -c COBOL, normal format
+ -p PL/I
+ 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
- -c2 COBOL compact format
+ -s SNOBOL
+ 1,10,55
- -c3 COBOL compact format extended
+ -u UNIVAC 1100 Assembler
+ 1,12,20,44
- -f FORTRAN
- -p PL/I
+
+ A few terminals provide the capability for changing their left/right
+ margins. The tabs program has an option to use this feature:
- -s SNOBOL
+ +mmargin
+ The effect depends on whether the terminal has the margin
+ capabilities:
- -u UNIVAC 1100 Assembler
+ o If the terminal provides the capability for setting the left
+ margin, tabs uses this, and adjusts the available width for
+ tab-stops.
+
+ o If the terminal does not provide the margin capabilities, tabs
+ imitates the effect, putting the tab stops at the appropriate
+ place on each line. The terminal's left-margin is not
+ modified.
+
+ If the margin parameter is omitted, the default is 10. Use +m0 to
+ reset the left margin, i.e., to the left edge of the terminal's
+ display. Before setting a left-margin, tabs resets the margin to
+ reduce problems which might arise on moving the cursor before the
+ current left-margin.
+
+ When setting or resetting the left-margin, tabs may reset the right-
+ margin.
- IEEEStd1003.1/TheOpenGroupBaseSpecificationsIssue7
- (POSIX.1-2008) describes a tabs utility. However
+ IEEEStd1003.1/TheOpenGroupBaseSpecificationsIssue7
+ (POSIX.1-2008) describes a tabs utility. However
- o This standard describes a +m option, to set a terminal's left-
+ o This standard describes a +m option, to set a terminal's left-
margin. Very few of the entries in the terminal database provide
- the smgl (set_left_margin) or smglp (set_left_margin_parm)
+ the smgl (set_left_margin) or smglp (set_left_margin_parm)
capability needed to support the feature.
- o There is no counterpart in X/Open Curses Issue 7 for this utility,
- unlike tput(1).
+ o There is no counterpart in X/Open Curses Issue 7 for this utility,
+ unlike tput(1).
- The -d (debug) and -n (no-op) options are extensions not provided by
+ The -d (debug) and -n (no-op) options are extensions not provided by
other implementations.
- A tabs utility appeared in PWB/Unix 1.0 (1977). There was a reduced
- version of the tabs utility in Unix 7th edition and in 3BSD (1979).
+ A tabs utility appeared in PWB/Unix 1.0 (1977). There was a reduced
+ version of the tabs utility in Unix 7th edition and in 3BSD (1979).
The latter supported a single "-n" option (to cause the first tab stop
to be set on the left margin). That option is not documented by POSIX.
- The PWB/Unix tabs utility, which was included in System III (1980),
+ The PWB/Unix tabs utility, which was included in System III (1980),
used built-in tables rather than the terminal database, to support a
- half-dozen terminal types. It also had built-in logic to support the
- left-margin, as well as a feature for copying the tab settings from a
- file.
+ half-dozen hardcopy terminal (printer) types. It also had built-in
+ logic to support the left-margin, as well as a feature for copying the
+ tab settings from a file.
Later versions of Unix, e.g., SVr4, added support for the terminal
- database, but kept the tables, as a fallback. In an earlier
- development effort, the tab-stop initialization provided by tset (1982)
- and incorporated into tput uses the terminal database,
-
- POSIX documents no limits on the number of tab stops. Documentation
+ database, but kept the tables to support the printers. In an earlier
+ development effort, the tab-stop initialization provided by tset (1982)
+ and incorporated into tput uses the terminal database,
+
+ The +m option was documented in the Base Specifications Issue 5
+ (Unix98, 1997), and omitted in Issue 6 (Unix03, 2004) without
+ documenting the rationale, though an introductory comment "and
+ optionallyadjuststhemargin" remains, overlooked in the removal. The
+ documented tabs utility in Issues 6 and later has no mechanism for
+ setting margins. The +m option in this implementation differs from the
+ feature in SVr4 by using terminal capabilities rather than built-in
+ tables.
+
+ POSIX documents no limits on the number of tab stops. Documentation
for other implementations states that there is a limit on the number of
- tab stops (e.g., 20 in PWB/Unix's tabs utility). While some terminals
- may not accept an arbitrary number of tab stops, this implementation
- will attempt to set tab stops up to the right margin of the screen, if
+ tab stops (e.g., 20 in PWB/Unix's tabs utility). While some terminals
+ may not accept an arbitrary number of tab stops, this implementation
+ will attempt to set tab stops up to the right margin of the screen, if
the given list happens to be that long.
- The Rationale section of the POSIX documentation goes into some detail
- about the ways the committee considered redesigning the tabs and tput
+ The Rationale section of the POSIX documentation goes into some detail
+ about the ways the committee considered redesigning the tabs and tput
utilities, without proposing an improved solution. It comments that
- no known historical version of tabs supports the capability of
+ no known historical version of tabs supports the capability of
setting arbitrary tab stops.
- However, the ExplicitLists described in this manual page were
- implemented in PWB/Unix. Those provide the capability of setting
+ However, the ExplicitLists described in this manual page were
+ implemented in PWB/Unix. Those provide the capability of setting
abitrary tab stops.