Remove lines from a file: Difference between revisions

=={{header|Nim}}==

<lang Nim>import sequtils, strutils

proc removeLines*(filename: string; start, count: Positive) =

# Read the whole file, split into lines but keep the ends of line.

var lines = filename.readFile().splitLines(keepEol = true)

# Remove final empty string if any.

if lines[^1].len == 0: lines.setLen(lines.len - 1)

# Compute indices and check validity.

let first = start - 1

let last = first + count - 1

if last >= lines.len:

raise newException(IOError, "trying to delete lines after end of file.")

# Delete the lines and write the file.

lines.delete(first, last)

filename.writeFile(lines.join())