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Tags that jump to line and column

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created 2003 · complexity basic · version 6.0

Programmers often use a tool like ctags to create a tags file that contains an index that allows Vim to jump to a particular location in a file when given a tag such as a function name (the index typically identifies where the function is defined). Sometimes a program is written to generate a tags file for a custom requirement. This tip shows that such a program can allow Vim to jump to a particular line and column in order to position the cursor on the wanted character.

Tags format

A tags file can be created with lines like the following (each line consists of three fields, separated by tab characters, although spaces are used for simplicity here):

first    one.txt   /\%12l\%34c/
second   two.txt   /\%1200l\%56c/

These define two tags: tag first refers to file one.txt at line 12, column 34 (where 1 is the first line and the first column). The last field is a search pattern where \%12l identifies line 12 and \%34c identifies column 34.


Usually a language like Python would be used to generate a tags file, but Vim script can do the job, although more slowly. To illustrate the process, the following script reads specified files and generates a tags file that indexes every word in each file.

" Read file and search each line for all occurrences of pattern.
" Return list of search hits.
" Each item in list is a list: [linenr, colnr, match]
function! SearchFile(file, pattern)
  let results = []
  let lines = readfile(a:file)
  for linenr in range(len(lines))
    let line = lines[linenr]
    let i = 1
    while 1
      let p1 = match(line, a:pattern, 0, i)
      if p1 < 0
      let p2 = matchend(line, a:pattern, 0, i)
      call add(results, [linenr+1, p1+1, strpart(line, p1, p2-p1)])
      let i += 1
  return results

" Search each file in filespec (e.g. '*.txt') for all occurrences of pattern.
" Return list of lines suitable for a tags file.
function! MakeTags(filespec, pattern)
  let tags = []
  for file in glob(a:filespec, 0, 1)
    for hit in SearchFile(file, a:pattern)
      call add(tags, printf("%s\t%s\t/\\%%%dl\\%%%dc/", hit[2], file, hit[0], hit[1]))
  return sort(tags)

The above script can be used like this:

call setline(1, MakeTags('*.txt', '\<\h\w*'))

All *.txt files in the current directory are searched, and each hit (matching text, file, line, column) creates an item in the resulting tags file. The example places the tags lines in a new buffer, which would generally be saved to a file called tags (no extension). Each line will be similar to the example shown earlier.

The pattern \<\h\w* finds all words (actually program identifiers): \< is the beginning of a word; \h is [A-Za-z_]; \w is [0-9A-Za-z_].


In example "function! SearchFile(file, pattern)" there is while loop with condition "while 1". Is is condition a mistake or I do not understand something, this condition seems to be true forever and the loop will never end, or I do not see something ?

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