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Top Forums Programming Memory allocation for particular process in UNIX Post 302936598 by Corona688 on Thursday 26th of February 2015 02:12:08 PM
Old 02-26-2015
Quote:
Originally Posted by kbw
C does have a "virtual machine".
It has a real machine. Smilie

Quote:
The C virtual machine has a call stack and a heap formed at opposite ends of the same memory block. The stack may have a fixed size, but the heap is everything else.
It's not really a block of memory. It's all translated from virtual addresses to real addresses. Both the stack and the heap are automatically "sized" through the magic of virtual memory. The kernel itself, behind the scenes, cares very little about which is which -- it just assigns memory in fixed-sized blocks from the pile. See The Paging Game for a general explanation on how paging works.

Quote:
If you need memory you use it and hand it back when done.
Agreed. There's no java VM to worry about, only the kernel itself. You use it, and the kernel either lets you or not.

It doesn't get "handed back", though. Your program keeps it for later, just in case you need to allocate again -- this makes it faster, and probably why he wanted to preallocate, but the kernel handles this for you.

Quote:
There's no portable way to put an upper limit on the heap.
Check out setrlimit.
 

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SHELL-QUOTE(1p) 					User Contributed Perl Documentation					   SHELL-QUOTE(1p)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.8.4 2005-05-03 SHELL-QUOTE(1p)
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