totty

totty unclogs pipes and gets them flowing again.

The standard I/O functions in libc will detect when a program is not writing to a terminal (also called a tty) and will automatically buffer output. While this is good for performance it can break the interactivity of a piped command that you're watching at the terminal.

Add the word totty (as in, "to a terminal") before any command in your pipe and that command will believe it is writing to a terminal, disabling the automatic buffering feature.

An example

A common command is:

tail -f /var/log/apache2/access.log | grep 404

but if a second grep is added, the output stops until the buffer fills:

tail -f /var/log/apache2/access.log | grep 404 | grep favicon.ico

To fix this, use totty and the pipe flows again!

tail -f /var/log/apache2/access.log | totty grep 404 | grep favicon.ico

No need to figure out which component is the source of the clog! It's safe to add it everywhere:

totty tail -f /var/log/apache2/access.log | totty grep 404 | totty grep favicon.ico

Alternatives

You may see suggestions to use the script command with particular flags for this purpose: script --return -c "command to execute" /dev/null. This has several downsides:

• it can be hard to remember the exact invocation
• it requires you to quote/escape the command to invoke
• it is not portable (none of the flags are supported on macOS)
• it's long and ugly

By comparison, totty works anywhere that supports POSIX pseudo-terminals, is easy to remember, is easy to introduce to a working pipe, and requires no escaping or modification of the pipe component that you're unclogging.