View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0001974 | 1003.1(2024)/Issue8 | Shell and Utilities | public | 2026-03-11 15:00 | 2026-03-11 19:39 |
| Reporter | mkoskar | Assigned To | |||
| Priority | normal | Severity | Objection | Type | Error |
| Status | New | Resolution | Open | ||
| Name | Miroslav Koškár | ||||
| Organization | |||||
| User Reference | |||||
| Section | 3 Utilities / tabs | ||||
| Page Number | 3415 | ||||
| Line Number | 116444-116446 | ||||
| Interp Status | |||||
| Final Accepted Text | |||||
| Summary | 0001974: tabs: wrong description of semantics of arbitrary tab stops | ||||
| Description | To get tab stops with a standard interval of 8: $ tabs -8 Analogous to that when arbitrary tab stops are used: $ tabs 1,9,17,25 Tab stop value: * is > 0 * represents a column (left-most being 1) where cursor moves and output occurs after preceding \t character * as a special case, the 1st tab stop value is always 1 (whether explicitly specified or not) to demonstrate that without preceding \t character output occurs in the left-most column The above is true for most common implementation of tabs from ncurses. I believe that indicated sentence: > 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. is wrong with regards to what actual semantics of operand(s) is. For additional context, this came up in following: * https://github.com/gwsw/less/issues/737 I've tried to summarize in following comment: * https://github.com/gwsw/less/issues/737#issuecomment-4033517061 Further of note are comments by @avih who were instrumental in tracking down historical sources of tabs and its documentation. | ||||
| Desired Action | Remove following sentence from the DESCRIPTION section: > 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. In OPERANDS section add following lines (demarcated with +++): 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. +++ A tab-stop value shall be taken to mean a column (left-most being 1) where cursor moves and output occurs after preceding \t character. The 1st tab-stop value is always 1 (whether explicitly specified or not) to demonstrate that without preceding \t character output occurs in the left-most column. +++ 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 "1 10 +10 +10" are considered to be identical. | ||||
| Tags | No tags attached. | ||||
|
|
Correction: I meant to reference following comment https://github.com/gwsw/less/issues/737#issuecomment-4030159904 instead. |
|
|
I think the terms left and right should be avoided, since such directions do not account for right-to-left scripts (in tbe Unicode sense of the term). "Beginning of line" and "end of line" might be better? |
|
|
Column-1 is the first available position for a tab stop on a line. An (ECMA-48 compatible) terminal can be set up so that the first tab stop on a line is not on the first column. The tabs program is documented to take this into account. Given that (and spelling), the sentence "The 1st tab-stop value is always 1 (whether explicitly specified or not) to demonstrate that without preceding \t character output occurs in the left-most column." needs some revision. Rather than removing the obscurely-worded sentence with "tabbing to position N", it should be revised to explain that tab-stops are 1-based, and that while the interval between stops may be 8, the 1-based detail makes the stops one column past the simple multiple of the tab interval. (making that both concise and clear doesn't look simple -- but the existing description is concise) |
