X-Git-Url: https://ncurses.scripts.mit.edu/?p=ncurses.git;a=blobdiff_plain;f=doc%2Fhtml%2Fman%2Ftabs.1.html;h=b921bf8570da9e2aabe4da1b60b83da7bc99b99b;hp=f957805c43638609b5177269de2004a498ca44e0;hb=51a395aaa20e4aa687310bb8cb1616ccf8e8fd0d;hpb=d66080c21038ad4feb2e41a0c4e517d5b4a03ab2
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+++ b/doc/html/man/tabs.1.html
@@ -1,6 +1,6 @@
@@ -34,7 +34,7 @@
tabs 1
-
+
@@ -66,6 +66,18 @@
ing the tabstops), and later cat the file to the screen, setting tab-
stops at that point.
+ These are hardware tabs, which cannot be queried rapidly by applica-
+ tions running in the terminal, if at all. Curses and other full-screen
+ applications may use hardware tabs in optimizing their output to the
+ terminal. If the hardware tabstops differ from the information in the
+ terminal database, the result is unpredictable. Before running curses
+ programs, you should either reset tab-stops to the standard interval
+
+ tabs -8
+
+ or use the reset program, since the normal initialization sequences do
+ not ensure that tab-stops are reset.
+
- IEEE Std 1003.1/The Open Group Base Specifications Issue 7
+ IEEEStd1003.1/TheOpenGroupBaseSpecificationsIssue7
(POSIX.1-2008) describes a tabs utility. However
o This standard describes a +m option, to set a terminal's left-mar-
- gin. Very few of the entries in the terminal database provide this
- capability.
+ gin. Very few of the entries in the terminal database provide 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,
+ 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.
- Documentation for other implementations states that there is a limit on
- the number of tab stops. While some terminals may not accept an arbi-
- trary 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.
+ A tabs utility appeared in PWB/Unix 1.0 (1977), and thereafter in 3BSD
+ (1979). It 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.
+ Initially, tabs 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 set-
+ tings 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 develop-
+ ment 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
+ for other implementations states that there is a limit on the number of
+ tab stops. 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
+ utilities, without proposing an improved solution. It comments that
+
+ no known historical version of tabs supports the capability of
+ setting arbitrary tab stops.
+
+ However, the ExplicitLists described in this manual page were imple-
+ mented in PWB/Unix. Those provide the capability of setting abitrary
+ tab stops.
tset(1), infocmp(1m), curses(3x), terminfo(5).
- This describes ncurses version 6.1 (patch 20180127).
+ This describes ncurses version 6.1 (patch 20190615).