sponge
Soak up stdin before writing to file
TLDR
Overwrite file with pipeline output
$ cat [file.txt] | sort | sponge [file.txt]
Filter and save in place$ grep "[pattern]" [file.txt] | sponge [file.txt]
Transform and overwrite$ sed 's/old/new/g' [file.txt] | sponge [file.txt]
Append instead of overwrite$ echo "new line" | sponge -a [file.txt]
SYNOPSIS
sponge [options] file
DESCRIPTION
sponge reads standard input and writes to a file. Unlike shell redirection, it reads all input before opening the output file, allowing safe in-place modifications.The tool is part of moreutils and solves the problem of using a file as both input and output in a pipeline.
PARAMETERS
-a
Append to file instead of overwriting.
EXAMPLES
Without sponge (fails):
$ sort file.txt > file.txt # Results in empty file!
With sponge (works):$ sort file.txt | sponge file.txt
INSTALL
sudo apt install moreutils
sudo dnf install moreutils
sudo pacman -S moreutils
sudo apk add moreutils
sudo zypper install moreutils
brew install moreutils
nix profile install nixpkgs#moreutils
CAVEATS
Loads entire input into memory. Very large files may exhaust memory. Part of moreutils package. Creates a temp file internally and renames it atomically when possible. If no file is specified, sponge outputs to stdout.
HISTORY
sponge is part of moreutils, a collection of Unix tools created by Joey Hess. It addresses a common shell scripting pitfall where redirection to the input file truncates it before reading.
