- set tabs on a terminal
tabs [-n | --file [[-code] | -a | -a2 | -c | -c2 | -c3 | -f | -p | -s | -u]] q!! [+m [n]] [-T type]
tabs [-T type] [+ m [n]] n1 [, n2 ,...]
The tabs utility sets the tab stops on the user's terminal according to a tab specification, after clearing any previous settings. The user's terminal must have remotely settable hardware tabs.
The following options are supported. If a given flag occurs more than once, the last value given takes effect:
tabs needs to know the type of terminal in order to set tabs and margins. type is a name listed in term(5). If no -T flag is supplied, tabs uses the value of the environment variable TERM. If the value of TERM is NULL or TERM is not defined in the environment (see environ(5)), tabs uses ansi+tabs as the terminal type to provide a sequence that will work for many terminals.
The margin argument may be used for some terminals. It causes all tabs to be moved over n columns by making column n+1 the left margin. If +m is given without a value of n, the value assumed is 10. For a TermiNet, the first value in the tab list should be 1, or the margin will move even further to the right. The normal (leftmost) margin on most terminals is obtained by +m0. The margin for most terminals is reset only when the +m flag is given explicitly.
Four types of tab specification are accepted. They are described below: canned, repetitive (-n), arbitrary (n1,n2,...), and file (–file).
If no tab specification is given, the default value is -8, that is, UNIX system ``standard'' tabs. The lowest column number is 1. Note: For tabs, column 1 always refers to the leftmost column on a terminal, even one whose column markers begin at 0, for example, the DASI 300, DASI 300s, and DASI 450.
Use one of the codes listed below to select a canned set of tabs. If more than one code is specified, the last code option will be used. The legal codes and their meanings are as follows:
1,10,16,36,72 Assembler, IBM S/370, first format
Assembler, IBM S/370, second format
COBOL, normal format
COBOL compact format (columns 1-6 omitted). Using this code, the first typed character corresponds to card column 7, one space gets you to column 8, and a tab reaches column 12. Files using this tab setup should include a format specification as follows (see fspec(4)):
<:t-c2 m6 s66 d:>
COBOL compact format (columns 1-6 omitted), with more tabs than -c2. This is the recommended format for COBOL. The appropriate format specification is (see fspec(4)):
<:t-c3 m6 s66 d:>
UNIVAC 1100 Assembler
A repetitive specification requests tabs at columns 1+n, 1+2*n, etc., where n is a single-digit decimal number. Of particular importance is the value 8: this represents the UNIX system ``standard'' tab setting, and is the most likely tab setting to be found at a terminal. When -0 is used, the tab stops are cleared and no new ones are set.
If the name of a file is given, tabs reads the first line of the file, searching for a format specification (see fspec(4)). If it finds one there, it sets the tab stops according to it, otherwise it sets them as -8. This type of specification may be used to make sure that a tabbed file is printed with correct tab settings, and would be used with the pr command:
example% tabs – file; pr file
Tab and margin setting is performed via the standard output.
The following operand is supported:
The arbitrary format consists of tab-stop values separated by commas or spaces. The tab-stop values must be positive decimal integers in ascending order. Up to 40 numbers are allowed. 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. Thus, the formats 1,10,20,30, and 1,10,+10,+10 are considered identical.
示例 1 Using the tabs command
The following command is an example using -code ( canned specification) to set tabs to the settings required by the IBM assembler: columns 1, 10, 16, 36, 72:
example% tabs -a
The next command is an example of using -n (repetitive specification), where n is 8, causes tabs to be set every eighth position: 1+(1*8), 1+(2*8), . . . which evaluate to columns 9, 17, . . . :
example% tabs -8
This command uses n1,n2,. . . (arbitrary specification) to set tabs at columns 1, 8, and 36:
example% tabs 1,8,36
The last command is an example of using –file (file specification) to indicate that tabs should be set according to the first line of $HOME/fspec.list/att4425 (see fspec(4)).
example% tabs –$HOME/fspec.list/att4425
See environ(5) for descriptions of the following environment variables that affect the execution of tabs: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.
Determine the terminal type. If this variable is unset or null, and if the -T option is not specified, terminal type ansi+tabs will be used.
The following exit values are returned:
An error occurred.
See attributes(5) for descriptions of the following attributes:
There is no consistency among different terminals regarding ways of clearing tabs and setting the left margin.
tabs clears only 20 tabs (on terminals requiring a long sequence), but is willing to set 64.
The tabspec used with the tabs command is different from the one used with the newform command. For example, tabs -8 sets every eighth position; whereas newform -i-8 indicates that tabs are set every eighth position.