Command line

npx line-seeker <file> [options]

Use - as <file> to read stdin (stream only; no index).

--line <n>           print one line (negative = from EOF)
--locate <n>         print JSON { line, lineNumber, offset, nextOffset }
--around <n>         print a window around a line
--before <n>         lines before a --grep / --around hit
--after <n>          lines after a --grep / --around hit
--range <a>-<b>      print an inclusive range
--copy <a>-<b>       stream a range to stdout (no maxRange cap)
--tail <n>           print the last n lines
--lines <n,n,n>      print scattered lines
--grep <pattern>     search (string or /regex/flags)
--matches <pattern>  print the hit count for a pattern
--limit <n>          max matches for --grep
--start <n>          start line for --grep
--end <n>            end line for --grep
--set <n>            replace line n (needs --with)
--insert <n>         insert before line n (needs --with)
--delete <a>[-<b>]   delete a line or inclusive range
--with <text>        payload for --set / --insert
--count              print the line count
--index              build a sidecar index
--refresh            extend an existing index after append
--stride <n>         index density (default 64)
--follow             print new lines as they arrive
--from-start         with --follow, replay the file first
--poll <ms>          follow poll interval (default 250)
--no-watch           follow: poll only, do not fs.watch
--encoding <enc>     line decoding (default utf8)
--index-path <path>  sidecar index location
--cache-index        store the index under the cache dir
--cache-dir <path>   override cache directory

Examples

npx line-seeker app.log --line 50
npx line-seeker app.log --locate 35495596
npx line-seeker app.log --around 35495596 --before 5 --after 5
npx line-seeker app.log --copy 1000000-1000200 > slice.log
npx line-seeker app.log --matches ERROR
npx line-seeker app.log --line -1
npx line-seeker app.log --range 100-105
npx line-seeker app.log --range -50--1
npx line-seeker app.log --tail 100
npx line-seeker app.log --lines 3,80,500000
npx line-seeker app.log --grep ERROR --limit 20
npx line-seeker app.log --grep '/ERROR|FATAL/i' --start 1 --end 10000
npx line-seeker app.log --count
npx line-seeker app.log --index --stride 64
npx line-seeker app.log --refresh
npx line-seeker notes.txt --set 3 --with "updated"
npx line-seeker notes.txt --insert 1 --with "# header"
npx line-seeker notes.txt --delete 2-4
cat app.log | npx line-seeker - --grep ERROR

--count prints a bare decimal. No color, so scripts can read it. Without an index this scans the file.

--grep writes one diagnostic line per hit. Exit code 1 if nothing matched. It is a JavaScript scan of decoded lines, not ripgrep.

--index prints the JSON build result (lineCount, entryCount, stride, …). That command reads the whole file once.

--set / --insert / --delete copy the file through a temp path. Cost follows file size, not the edited line.

A missing file is a single line on stderr, exit code 1, no Node stack.