Sponsored Content
Top Forums UNIX for Advanced & Expert Users Cmd 'cat /dev/urandom' not closing cleanly Post 302996550 by MadeInGermany on Thursday 27th of April 2017 07:11:05 AM
Old 04-27-2017
You are right that head should send a SIGPIPE to fold that should send a SIGPIPE to tr that should send a SIGPIPE to cat.
And each program in the chain should terminate.
It's not reliable though, a signal *can* get lost, especially if the system is very busy. If this also happens on an idle system then there is a bug somewhere (in one of the programs or in the shell's pipe handling).
In one of my old scripts (using /bin/sh for many LUnix platforms) I had limited it with
Code:
dd if=/dev/urandom dd bs=1 count=12000 | tr ...

and, for safety, if the resul string was too short, I repeated it in a loop.
 

8 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

/dev/urandom

Hi, how do I use /dev/urandom to generate a single number between 1-100? I can od /dev/urandom but it gives me an endless list of random numbers, I just want 1 between 1-100. How can I get that? Thanks. (12 Replies)
Discussion started by: Takumi
12 Replies

2. Solaris

What is /dev/tty /dev/null and /dev/console

Hi, Anyone can help My solaris 8 system has the following /dev/null , /dev/tty and /dev/console All permission are lrwxrwxrwx Can this be change to a non-world write ?? any impact ?? (12 Replies)
Discussion started by: civic2005
12 Replies

3. UNIX for Dummies Questions & Answers

cat /dev/null

Hi, Excuse my ignorance here - I'm a networks man and my knowledge of all things unix is somewhat limited. We have a very large file (/var/tmp/mond.log) that we need to zero - does the "cat /dev/null > /var/tmp/mond.log" command achieve this? (4 Replies)
Discussion started by: freakydancer
4 Replies

4. Slackware

Can't play sound files with aplay or cat to /dev/dsp

I am having problems using soundes. Until a few moments ago the following commands produced errors and no sound: cat /usr/share/apps/kolf/sounds/blackhole.wav/ > /dev/dsp yielded: /dev/dsp: Invalid argument cat /usr/share/apps/kolf/sounds/blackhole.wav > /dev/audio yelded: /dev/audio:... (3 Replies)
Discussion started by: slak0
3 Replies

5. Shell Programming and Scripting

Error output of cat to /dev/null

Hello, I'm trying to send the error output of a 'cat' operation to /dev/null like this: cat /dirA/dirB/temp*.log > /dirA/dirB/final.log 2>/dev/null This works perfectly in a terminal, but not when placed in a script. If there are no files matching temp*.log the script outputs an error... (7 Replies)
Discussion started by: Nils88
7 Replies

6. Shell Programming and Scripting

Memory fault(coredump) while using cat cmd

i have few log files that are input to my perl script... i am executing the script as below cat RTR*.log | test.pl and getting the following error -ksh: 25014: Memory fault(coredump) cat: write error: Connection reset by peer can anyone help me on this.... Thanks in... (2 Replies)
Discussion started by: niteesh_!7
2 Replies

7. UNIX for Beginners Questions & Answers

Cleanly log out a user w/o killing process

My AIX-based accounting program runs an end-of-day process that requires all users to be logged out. Sometimes I have a user that leaves for the day and forgets to logout. Is there any way I can cleanly log a user out without killing their process? (4 Replies)
Discussion started by: DLS1701
4 Replies

8. HP-UX

Dev/urandom and dev/random missing in HP-UX

Hi, In our HP-UX B.11.11. I could not find dev/urandom and dev/random Are all pseudo-devices implemented as device drivers, or in need to run /configure some package to install the package to have dev/urandom. Please help (4 Replies)
Discussion started by: rashi
4 Replies
MCOOKIE(1)						     Linux Programmer's Manual							MCOOKIE(1)

NAME
mcookie - generate magic cookies for xauth SYNOPSIS
mcookie [-v] [-f filename] DESCRIPTION
mcookie generates a 128-bit random hexadecimal number for use with the X authority system. Typical usage: xauth add :0 . `mcookie` The "random" number generated is actually the output of the MD5 message digest fed with various pieces of random information: the current time, the process id, the parent process id, the contents of an input file (if -f is specified), and several bytes of information from the first of the following devices which is present: /dev/random, /dev/urandom, files in /proc, /dev/audio. BUGS
The entropy in the generated 128-bit is probably quite small (and, therefore, vulnerable to attack) unless a non-pseudorandom number gener- ator is used (e.g., /dev/random under Linux). It is assumed that none of the devices opened will block. FILES
/dev/random /dev/urandom /dev/audio /proc/stat /proc/loadavg SEE ALSO
X(1), xauth(1), md5sum(1) AVAILABILITY
The mcookie command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/. 25 September 1995 MCOOKIE(1)
All times are GMT -4. The time now is 04:10 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy