jjlin / edln

A simple readline-based utility for interactively editing the target of a symbolic link

Introduction

edln is a simple readline-based utility for interactively editing the target of a symbolic link. This is most useful if you only need to make a relatively minor change to the symlink.

Using edln

Typically, edln is called with a single argument -- the path to the symlink to be edited. For example, if you have a symlink foo that points to the file /usr/local/bin/foo-1.0, and you want to update it to point to the file /usr/local/bin/foo-1.1 instead, you would invoke edln as follows (where the $ denotes the shell prompt):

  $ edln foo
  New target: /usr/local/bin/foo-1.0

As you can see, edln displays the current symlink target, and allows you to edit it. Now press the Backspace key once to delete the 0 character, then press the 1 key to insert the 1 character, and finally, press the Enter key to complete the update.

As edln relies on GNU Readline for editing, it supports much more sophisticated editing than demonstrated in the simple example above. Refer to the GNU Readline User Manual for further details:

https://tiswww.case.edu/php/chet/readline/rluserman.html

As a final note, edln also supports a two-argument invocation that is basically equivalent to ln -sfT. That is, edln foo /usr/local/bin/foo-1.1 has the same effect as ln -sfT /usr/local/bin/foo-1.1 foo.

Note that the -T option causes ln to behave differently when the symlink foo points to a directory. For example, suppose foo points to dir1, and you want to change it to point to dir2 instead. Running ln -sf dir2 foo will not accomplish this -- instead, it will create inside dir1 a new symlink dir2 (that points to dir2). In contrast, running edln foo dir2 or ln -sfT dir2 foo will have the desired effect.

Pre-Built Binaries

Binaries for CentOS and Ubuntu are available at:

https://github.com/jjlin/edln/releases

For other platforms, edln should not be difficult to build from source.

Building From Source

A simple makefile is provided with the edln source code, available at:

https://github.com/jjlin/edln/

You need to ensure that the GNU Readline development packages are installed (e.g., libreadline-dev on Debian/Ubuntu, or readline-devel on RHEL/CentOS).

You may also need to ensure that the GNU Ncurses package is installed, particularly on RHEL/CentOS, where linking with the -lncurses flag is required. On RHEL/CentOS, the package name is ncurses.

Exact details for building from source on other Unix-like systems may vary, but should be quite similar.