Append_file!

append_file! adds text to the end of a file without replacing its existing contents.

Overview

Use append_file! when a file should keep its current contents and receive additional text.

append_file!("logs/adventure.log", "Entered the crystal caves\n")

append_file!("logs/adventure.log", "Entered the crystal caves\n")

If adventure.log already contains text, the new line is written after it.

If the file does not exist, Goblin creates it.

It Does Not Add a Newline

append_file! writes the text exactly as provided. Add \n yourself when appending lines:

append_file!("logs/adventure.log", "Found the hidden gate\n")
append_file!("logs/adventure.log", "Opened the gate\n")

append_file!("logs/adventure.log", "Found the hidden gate\n")
append_file!("logs/adventure.log", "Opened the gate\n")

Without the newline characters, the text is joined together:

append_file!("notes.txt", "north")
append_file!("notes.txt", "tunnel")

/// notes.txt now contains: northtunnel

append_file!("notes.txt", "north")
append_file!("notes.txt", "tunnel")

/// notes.txt now contains: northtunnel

Mutation Form Required

Appending changes the filesystem, so append_file requires the ! form:

append_file!("notes.txt", "Bring more rope\n")

append_file!("notes.txt", "Bring more rope\n")

Calling it without ! raises an error:

append_file("notes.txt", "Bring more rope\n")
/// error: M0001 mutation-operator-required

append_file("notes.txt", "Bring more rope\n")
/// error: M0001 mutation-operator-required

Signature

append_file!(path, text)

append_file!(path, text)

append_file! returns unit.

The file is created when it is missing, but its parent directory must already exist.

Errors

append_file! requires exactly two arguments:

append_file!("notes.txt")
/// error: R0301 wrong-arity

append_file!("notes.txt")
/// error: R0301 wrong-arity

Both arguments must be strings:

append_file!("notes.txt", 42)
/// error: T0205 type-mismatch

append_file!("notes.txt", 42)
/// error: T0205 type-mismatch

Goblin raises a filesystem error if it cannot open or write to the file:

FS0001 filesystem-io

FS0001 filesystem-io

This can happen when the parent directory is missing, permissions deny access, or the disk cannot accept more data.