---
name: "erl_comment_scan"
section: "3erl"
platform: "linux"
package: "erlang-manpages"
version: "1:25.2.3+dfsg-1+deb12u4"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/erl_comment_scan"
---

# erl\_comment\_scan(3erl)

Functions for reading comment lines from Erlang source code.

## NAME

erl\_comment\_scan - Functions for reading comment lines from Erlang source code.

## DESCRIPTION

Functions for reading comment lines from Erlang source code.

## DATA TYPES

- **comment() = {Line::integer(), Column::integer(), Indentation::integer(), Text::\[string()\]}:**

  - **commentLine() = {Line::integer(), Column::integer(), Indent::integer(), Text::string()}:**

  ## EXPORTS

**file(Name::file:filename()) -\> \[comment()\]**\

Extracts comments from an Erlang source code file. Returns a list of entries representing *multi-line* comments, listed in order of increasing line-numbers. For each entry, *Text* is a list of strings representing the consecutive comment lines in top-down order; the strings contain *all* characters following (but not including) the first comment-introducing *%* character on the line, up to (but not including) the line-terminating newline.

Furthermore, *Line* is the line number and *Column* the left column of the comment (i.e., the column of the comment-introducing *%* character). *Indent* is the indentation (or padding), measured in character positions between the last non-whitespace character before the comment (or the left margin), and the left column of the comment. *Line* and *Column* are always positive integers, and *Indentation* is a nonnegative integer.

Evaluation exits with reason *{read, Reason}* if a read error occurred, where *Reason* is an atom corresponding to a Posix error code; see the module [file(3erl)](/file/3erl.md) for details.

**join\_lines(Lines::\[commentLine()\]) -\> \[comment()\]**\

Joins individual comment lines into multi-line comments. The input is a list of entries representing individual comment lines, *in order of decreasing line-numbers*; see scan\_lines/1 for details. The result is a list of entries representing *multi-line* comments, *still listed in order of decreasing line-numbers*, but where for each entry, *Text* is a list of consecutive comment lines in order of *increasing* line-numbers (i.e., top-down).

*See also:* scan\_lines/1.

**scan\_lines(Text::string()) -\> \[commentLine()\]**\

Extracts individual comment lines from a source code string. Returns a list of comment lines found in the text, listed in order of *decreasing* line-numbers, i.e., the last comment line in the input is first in the resulting list. *Text* is a single string, containing all characters following (but not including) the first comment-introducing *%* character on the line, up to (but not including) the line-terminating newline. For details on *Line*, *Column* and *Indent*, see file/1.

**string(Text::string()) -\> \[comment()\]**\

Extracts comments from a string containing Erlang source code. Except for reading directly from a string, the behaviour is the same as for file/1.

*See also:* file/1.

## AUTHORS

Richard Carlsson *\<carlsson.richard@gmail.com\>*