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Full Discussion: How to set font color for STDIN,STDOUT and STDERR?
Top Forums UNIX for Advanced & Expert Users How to set font color for STDIN,STDOUT and STDERR? Post 302542402 by Corona688 on Wednesday 27th of July 2011 12:27:16 PM
Old 07-27-2011
The terminal can't tell what's printing to standard output vs standard error -- they both go to literally the same file. You could intercept standard error with a fifo and process it...
Code:
#!/bin/bash

# On exit, close stderr and delete the fifo so we don't leave dangling background processes.
trap "exec 2<&- ; rm ~/.tmpfifo" EXIT

rm -f ~/.tmpfifo

mkfifo ~/.tmpfifo
# Create a subshell that reads from fifo, writes to stderr.
# it gets its own copy of stderr, so redirecting stderr later won't change this.
(       while read LINE
        do
                printf "\x1b[01;31m%s\x1b[01;m\n" "$LINE"
        done < ~/.tmpfifo ) &

exec 2>~/.tmpfifo

# Thing that should print standard error in red
touch /

Code:
$ ./errfilter.sh
touch: setting times of `/': Permission denied
$

This only works for scripts, not for interactive terminals, because bash frequently uses stderr for its own things when in interactive mode.

---------- Post updated at 10:27 AM ---------- Previous update was at 10:11 AM ----------

Actually, here's a way that'll work in interactive mode:

Code:
trap "exec 5>~/.tmpfifo-$$ ; rm -f ~/.tmpfifo-$$ ; exec 5<&-" EXIT

mkfifo ~/.tmpfifo-$$

(       while [ -e ~/.tmpfifo-$$ ]
        do
                while read LINE
                do
                        printf "\x1b[01;31m%s\x1b[01;m\n" "$LINE"
                done < ~/.tmpfifo-$$ >&2
        done
 ) &

function err
{
        "$@" 2>/.tmpfifo-$$
}

Do this in your shell:
Code:
$ source errfilter.sh
$ err touch /
touch: setting times of `/': Permission denied
$

and any commands you run with err will have stderr color-coded.
This User Gave Thanks to Corona688 For This Post:
ungalnanban
 

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LEARN ABOUT V7

fifo

fifo(3tcl)																fifo(3tcl)

NAME

       fifo - Create and manipulate u-turn fifo channels

SYNOPSIS

       package require Tcl

       package require memchan

       fifo

DESCRIPTION

       fifo   creates  a stream-oriented in-memory channel and returns its handle. There is no restriction on the ultimate size of the channel, it
	      will always grow as much as is necessary to accommodate the data written into it.

	      In contrast to the channels generated by memchan a channel created here effectively represents an U-turn. All data written  into	it
	      can be read out, but only in the same order. This also means that a fifo channel is not seekable.

	      The channels created here can be transferred between interpreters in the same thread and between threads, but only as a whole. It is
	      not possible to use them to create a bi- or unidirectional connection between two interpreters.

       Memory channels created by fifo provide two read-only options which can be queried via the standard fconfigure command. These are

       -length
	      The value of this option is the number of bytes currently stored in the queried memory channel.

       -allocated
	      The value of this option is the number of bytes currently allocated by the queried memory channel. This number is at least as big as
	      the value of -length.

       As  the	channels generated by fifo grow as necessary they are always writable. This means that a writable fileevent-handler will fire con-
       tinuously.

       The channels are also readable if they contain more than zero bytes. Under this conditions a readable fileevent-handler will fire  continu-
       ously.

NOTES

       One possible application of memory channels created by memchan or fifo is as temporary storage device to collect data coming in over a pipe
       or a socket. If part of the processing of the incoming data is to read and process header bytes or similar fifo are easier to use  as  they
       do not require seeking back and forth to switch between the assimilation of headers at the beginning and writing new data at the end.

SEE ALSO

       fifo2, memchan, null

KEYWORDS

       channel, fifo, i/o, in-memory channel, memchan, stream

COPYRIGHT

       Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>

Memory channels 							2.1								fifo(3tcl)
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