04-11-2007
Quote:
Originally Posted by porter
If you can't fork you can't run a command in a shell to see why it can't fork, as it needs to fork to create the process to run the command in.
First, reborg suggested arranging for a command to run every five minutes which might show /tmp filling prior to being totally filled. And it is possible for a large process to be unable to fork while smaller processes have no problem. This is actually quite common. Finally, it is not exactly true that a shell must fork to run a command. A shell is programming language with lots of built in commands. Can't launch ls?
$ myls() { while [ $# -ne 0 ] ; do echo "$1" ; shift ; done ; }
$ myls /etc/s*
/etc/services
/etc/shells
/etc/syslog.conf
$
Can't launch cat?
$ mycat() { while IFS="" read l ; do echo "$l" ; done < $1 ; }
$ mycat /etc/shells
#
# This is a list of valid login shells (single rooted).
# Ftpd must see one of these shells as a user's login shell to connect.
#
/bin/sh
/bin/ksh
/bin/csh
/bin/tcsh
/usr/local/bin/bash
$
None of that needed a single fork provided I use ksh. I can conjure up limited versions of quite a few commands this way. And if I am desperate to diagnose a stalled OS before I cycle power, I have a final trick...I can run a single command by using exec...
exec df -k
A box that cannot fork can often exec.
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LEARN ABOUT DEBIAN
libbash
LIBBASH(7) libbash Manual LIBBASH(7)
NAME
libbash -- A bash shared libraries package.
DESCRIPTION
libbash is a package that enables bash dynamic-like shared libraries. Actually its a tool for managing bash scripts whose functions you may
want to load and use in scripts of your own.
It contains a 'dynamic loader' for the shared libraries ( ldbash(1)), a configuration tool (ldbashconfig(8)), and some libraries.
Using ldbash(1) you are able to load loadable bash libraries, such as getopts(1) and hashstash(1). A bash shared library that can be loaded
using
ldbash(1) must answer 4 requirments:
1. It must be installed in $LIBBASH_PREFIX/lib/bash (default is /usr/lib/bash).
2. It must contain a line that begins with '#EXPORT='. That line will contain (after the '=') a list of functions that the library
exports. I.e. all the function that will be usable after loading that library will be listed in that line.
3. It must contain a line that begins with '#REQUIRE='. That line will contain (after the '=') a list of bash libraries that are
required for our library. I.e. every bash library that is in use in our bash library must be listed there.
4. The library must be listed (For more information, see ldbashconfig(8)).
Basic guidelines for writing library of your own:
1. Be aware, that your library will be actually sourced. So, basically, it should contain (i.e define) only functions.
2. Try to declare all variables intended for internal use as local.
3. Global variables and functions that are intended for internal use (i.e are not defined in '#EXPORT=') should begin with:
__<library_name>_
For example, internal function myfoosort of hashstash library should be named as
__hashstash_myfoosort
This helps to avoid conflicts in global name space when using libraries that come from different vendors.
4. See html manual for full version of this guide.
AUTHORS
Hai Zaar <haizaar@haizaar.com>
Gil Ran <ril@ran4.net>
SEE ALSO
ldbash(1), ldbashconfig(8), getopts(1), hashstash(1) colors(1) messages(1) urlcoding(1) locks(1)
Linux Epoch Linux