Solving real-world problems with Linux's proc filesystem

Post by gnosis » Tue, Jan 11, 2011, 4:36 PM UTC

In the "redirect harder" section, the solution given to a program that needs an explicitly named file for standard input is:

  echo hello | python crap-prog.py /proc/self/fd/0

In zsh the same thing can be accomplished with a more concise syntax:

  python crap-prog.py


And, if your process wanted to seek the file (which isn't possible to do with a simple redirection of stdin), you could do:
  python crap-prog.py =(echo hello)

The main difference is that here, behind the scenes zsh creates and deletes a temporary file with the contents of the stdout of the program between the =().Another neat thing you can do in zsh to solve the original problem is to create a global alias for stdin:
  alias -g STDIN=/proc/self/fd/0

Then, whenever you typed "STDIN" on the command line, zsh would convert it to "/proc/self/fd/0".  Then to make the exact equivalent of the original solution (but one that's easier to remember and type), you could simply write:
  echo hello | python crap-prog.py STDIN

A regular alias won't work here, since regular aliases only expand when they're the first part of a command.  Global aliases will expand anywhere in the command line.  So you just have to be a bit more careful with them.---
The solution in the "phantom progress bar" section is cute, and a good demonstration of what's possible to do with /proc/$PID/fdinfo, but you could just use a ready made solution like either of these:
http://clpbar.sourceforge.net/
http://www.ivarch.com/programs/pv.shtml

Solving real-world problems with Linux's proc filesystem

Re: Solving real-world problems with Linux's proc filesystem

Re: Solving real-world problems with Linux's proc filesystem