Grab exactly one byte from a FIFO, at random intervals Post: 302747901

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Top Forums Shell Programming and Scripting Grab exactly one byte from a FIFO, at random intervals Post 302747901 by vomv1988 on Sunday 23rd of December 2012 04:34:44 PM

12-23-2012

Registered User

I'm currently using bash in a mac, but I was testing the code from the original post also in GNU/Linux, in bash too.

I see how several unterminated instances of the 'listen' section would cause the behavior. I used ps to check, and killed all undesired instances of the listen section, but that didn't seem to solve it. So I split the script into two scripts:

listen.sh

Code:

#!/bin/bash

# Listen

	IFS=
	tail -f INPUT | while read -n 1 CHAR ; do
		printf "${CHAR}" > FIFO
#		sleep 0.2
	done

EDIT: The behavior only happens without the sleep delay. But I would like to have a working script that does not require the sleep delay.

prompt.sh

Code:

#!/bin/bash

PROMPT=n
while test ${PROMPT} != 'q' ; do
	printf 'y: print next byte\nn: don'"'"'t print next byte\nq: quit\n'
	read -n 1 PROMPT
	printf '\n'
	if test "${PROMPT}" = 'y' ; then

# Grab 1 byte

		BYTE=`cat FIFO`
		printf 'The input byte is:\n'
		printf "${BYTE}" | xxd -cols 1
	fi
done

So, on one terminal, I run ./listen.sh, and I leave it there, on a second one, I run ./prompt.sh, and leave it there also, and finally, on a third terminal, I run "printf 'Hello, world!' > INPUT".

I go back to the second terminal, and type 'y', and get the same undesired behavior. This time, I made sure there were no undesired unterminated instances of the listen section. bipinajith: Are you using the exact same code from my original post, or did you add any changes to yours?

vomv1988

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apropos

apropos(1)							   User Commands							apropos(1)

NAME

       apropos - locate commands by keyword lookup

SYNOPSIS

       apropos keyword...

DESCRIPTION

       The apropos utility displays the man page name, section number, and a short description for each man page whose NAME line contains keyword.
       This information is contained in the /usr/share/man/windex database created by catman(1M). If catman(1M) was not run, or was run  with  the
       -n  option,  apropos  fails. Each word is considered separately and the case of letters is ignored. Words which are part of other words are
       considered; for example, when looking for `compile', apropos finds all instances of `compiler' also.

       apropos is actually just the -k option to the man(1) command.

EXAMPLES

       Example 1: To find a man page whose NAME line contains a keyword

       Try

       example% apropos password

       and

       example% apropos editor

       If the line starts `filename(section) ...' you can run

       man -s section filename
       to display the man page for filename.

       Example 2: To find the man page for the subroutine printf()

       Try

       example% apropos format

       and then

       example% man -s 3s printf

       to get the manual page on the subroutine printf().

FILES

       /usr/share/man/windex	       table of contents and keyword database

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWdoc			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       man(1), whatis(1), catman(1M), attributes(5)

DIAGNOSTICS

       /usr/share/man/windex: No such file or directory

	   This database does not exist. catman(1M) must be run to create it.

SunOS 5.10							    20 Dec 1996 							apropos(1)