Rlwrap: A Readline Wrapper

rlwrap v 0.46 October 2022

WHAT IT IS:

rlwrap is a 'readline wrapper', a small utility that uses the GNU Readline library to allow the editing of keyboard input for any command.

I couldn't find anything like it when I needed it, so I wrote this one back in 1999. By now, there are (and, in hindsight, even then there were) a number of good readline wrappers around, like rlfe, distributed as part of the GNU readline library, and the amazing socat.

You should consider using rlwrap especially when you need user-defined completion (by way of completion word lists) and persistent history, or if you want to program 'special effects' using the filter mechanism.

As it is often used with older or even obsolete software, rlwrap strives to compile and run on a fairly wide range of not necessarily recent Unix-like systems (FreeBSD, OSX, HP-UX, AIX, Solaris, QNX, cygwin, linux and probably quite a few more) This would not have been without Polarhome's now retired 'dinosaur zoo' of ageing Unix systems

HOW TO USE IT:

If

displays the infamous ^[[D when you press a left arrow key, or if you just want decent input history and completion, try:

$ rlwrap [-options] <command> <args>

You should not notice any difference compared to directly calling <command> <args>, except that you now can edit <command>'s input and recall its entire input history using the arrow keys.

Input history is remembered accross invocations, separately for different <command>s. CTRL-R will search the input history, like in bash. With the -r and -f options you can specify the list of words which rlwrap will use as possible completions, taking them from a file (-f option) or from <command>'s past in/output (-r option).

rlwrap continually monitors <command>'s terminal settings, so that it can do the right thing when it asks for single keypresses or for a password.

Commands that already use Readline, or a similar library, will always ask for (and get) single keypresses, so that rlwrapping them doesn't have any noticeable effect. To overcome this, one can use rlwrap with the --always-readline (-a) option; rlwrap will then use its own line editing and history. Unforunately, in that case, rlwrap cannot detect whether <command> asks for a password. This can be remedied by giving the password prompt (excluding trailing space and possibly the first few letters) as an argument to the -a option.

EXAMPLES:

Run netcat with command-line editing:

Run lprolog and use its saved input history and lib.pl to build a completion word list:

rlwrap -f lib.pl -f . lprolog

Run smbclient (which already uses readline), add all input and output to the completion list, complete local filenames, avoid showing (and storing) passwords:

rlwrap -cra -assword: smbclient '\\PEANUT\C' 

INSTALLATION:

Usually just

./configure;
make
sudo make install

See the INSTALL file for more information.

FILTERS

Filters are perl or python plugins that enable complete (albeit somewhat fragile) control over rlwrap's input and output, echo, prompt, history and completion. They aren't used a lot, and remain therefore somewhat untested. rlwrap -z listing lists the installed filters, rlwrap -z <somefilter> displays a short help text for <somefilter>

AUTHORS

The GNU Readline library (written by Brian Fox and Chet Ramey) does all the hard work behind the scenes, the pty-handling code (written by Geoff C. Wing) was taken practically unchanged from rxvt, and completion word lists are managed by Damian Ivereigh's libredblack library. The rest was written by Hans Lub (hanslub42@gmail.com).

HOMEPAGE

https://github.com/hanslub42/rlwrap

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