File::Prepend::Undoable - Prepend string to a file, with undo support


This document describes version 0.04 of File::Prepend::Undoable (from Perl distribution File-Prepend-Undoable), released on 2015-09-03.




prepend(%args) -> [status, msg, result, meta]

Prepend string to a file, with undo support.

On do, will trash file, copy it to original location (with the same permission and ownership as the original) and prepend the string to the beginning of file. On undo will trash the new file and untrash the original.

Some notes:

  • Chown will not be done if we are not running as root.

  • Symlink is currently not permitted.

  • Since transaction requires the function to be idempotent, in the check_state phase the function will check if the string has been prepended. It will refuse to prepend the same string twice.

  • Take care not to use string that are too large, as the string, being a function parameter, is entered into the transaction table.

Fixed state: file exists and string has been prepended to beginning of file.

Fixable state: file exists and string has not been prepended to beginning of file.

Unfixable state: file does not exist or path is not a regular file (directory and symlink included).

This function is idempotent (repeated invocations with same arguments has the same effect as single invocation). This function supports transactions.

Arguments ('*' denotes required arguments):

  • path* => str

    The file to prepend.

  • string* => any

    The string to prepend to file.

Special arguments:

Returns an enveloped result (an array).

First element (status) is an integer containing HTTP status code (200 means OK, 4xx caller error, 5xx function error). Second element (msg) is a string containing error message, or 'OK' if status is 200. Third element (result) is optional, the actual result. Fourth element (meta) is called result metadata and is optional, a hash that contains extra information.

Return value: (any)


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