Visit Our UNIX and Linux User Community


Array size


 
Thread Tools Search this Thread
Top Forums Programming Array size
# 1  
Old 07-31-2001
Array size

In a C program is there any limit on the size of an array?
# 2  
Old 07-31-2001
array size

I will say Yes, there is limitation of array size.
However, this will base on O.S and memory.

Let's say you have 4Gb Virtual Mem; it does not mean you can use all of them (i.e. some of them reserved for thread frames...)

If you need to know more details, you may want to go through some O.S internal books.

hope this help

Smilie
# 3  
Old 08-01-2001
When a new process is created it is not given unlimited memory. Much of the memory requirements come from symbols created during compile time based on memory allocation requirements. Examples in C include the malloc system call, memory allocation.

So, the size of any array is contrained by how much space for that array was malloc'ed for example, when the binary was compiled and process executed.

Hope this helps.

Quote:
MALLOC(3) Linux Programmer's Manual MALLOC(3)

NAME
calloc, malloc, free, realloc - Allocate and free dynamic
memory

SYNOPSIS
#include <stdlib.h>

void *calloc(size_t nmemb, size_t size);
void *malloc(size_t size);
void free(void *ptr);
void *realloc(void *ptr, size_t size);

DESCRIPTION
calloc() allocates memory for an array of nmemb elements
of size bytes each and returns a pointer to the allocated
memory. The memory is set to zero.

malloc() allocates size bytes and returns a pointer to the
allocated memory. The memory is not cleared.

( ..... extract from man page ... )
# 4  
Old 08-26-2001
limits on array sizes

The answer is No and Yes. Theoretically,
there is no limit. However, the kernel may be
configured to allow only a limited amount
of memory per process and/or user. You can find
out what the system resource limits are on your
particular UNIX system using the system
call "getrlimit()" (man section 2). The following
C program can be compiled and run as any ordinary
user...

================== SNIP ========================
/*
* Filename - getlimits.c
*
* Description - display system resource limits and
* test allocating large blocks of memory.
*
*/

#include <sys/time.h>
#include <sys/resource.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

main(int argc, char **argv)
{
struct rlimit rlim;
void *p;

getrlimit(RLIMIT_CPU, &rlim);
printf("CPU: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_FSIZE, &rlim);
printf("FSIZE: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_DATA, &rlim);
printf("DATA: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_STACK, &rlim);
printf("STACK: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_CORE, &rlim);
printf("CORE: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
#ifdef LINUX
getrlimit(RLIMIT_RSS, &rlim);
printf("RSS: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_NPROC, &rlim);
printf("NPROC: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
#else
getrlimit(RLIMIT_VMEM, &rlim);
printf("VMEM: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
getrlimit(RLIMIT_AS, &rlim);
printf("AS: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
#endif
getrlimit(RLIMIT_NOFILE, &rlim);
printf("NOFILE: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
#ifdef LINUX
getrlimit(RLIMIT_MEMLOCK, &rlim);
printf("MEMLOCK: cur - %ld max - %ld\n", rlim.rlim_cur, rlim.rlim_max);
#endif

if((p = malloc(100000000)) == NULL)
{
printf("malloc 100M failed\n");
}
else
{
printf("malloc 100M succeeded\n");
}
if(p) free(p);
if((p = malloc(500000000)) == NULL)
{
printf("malloc 500M failed\n");
}
else
{
printf("malloc 500M succeeded\n");
}
if(p) free(p);
return 0;
}

================== SNIP ========================

The output (on Linux) should look somthing like...

$ getlimits
CPU: cur - 2147483647 max - 2147483647
FSIZE: cur - 2147483647 max - 2147483647
DATA: cur - 2147483647 max - 2147483647
STACK: cur - 8388608 max - 2147483647
CORE: cur - 1024000000 max - 2147483647
RSS: cur - 2147483647 max - 2147483647
NPROC: cur - 2048 max - 2048
NOFILE: cur - 1024 max - 1024
MEMLOCK: cur - 2147483647 max - 2147483647
malloc 100M succeeded
malloc 500M succeeded
# 5  
Old 08-26-2001
the includes for the getlimits.c code

For some reason, the include files didn't
come out in the code in the previous posting.
the files are...

sys/time.h
sys/resource.h
unistd.h
stdio.h
stdlib.h

Previous Thread | Next Thread
Test Your Knowledge in Computers #101
Difficulty: Easy
Linux is fundamentally a UNIX clone written from scratch by Linus Torvalds with the help of many coders across the globe.
True or False?

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Array size in C shell scripting

Hi, I would like to know how to define the size of the array in c shell scripting. (15 Replies)
Discussion started by: gopishrine
15 Replies

2. Programming

Php number array from max, min, step size mysql data

I want to create a form with data values in a dropdown list. The values in the dropdown list need to be generated on the fly from max, min and increment values contained in a mysql database. Hopefully this makes sense, I really have no idea where to start :confused: Thanks (6 Replies)
Discussion started by: barrydocks
6 Replies

3. UNIX for Advanced & Expert Users

Physical disk IO size smaller than fragment block filesystem size ?

Hello, in one default UFS filesystem we have 8K block size (bsize) and 1K fragmentsize (fsize). At this scenary I thought all "FileSytem IO" will be 8K (or greater) but never smaller than the fragment size (1K). If a UFS fragment/blocksize is allwasy several ADJACENTS sectors on disk (in a ... (4 Replies)
Discussion started by: rarino2
4 Replies

4. Shell Programming and Scripting

Use Awk and Array to get total size of files

Hello all, I need to do scripts total up the size in selected extension file for example motion.mov and segmentation.avi is in Label Media. For file info.doc and calc.xls in Label Document. I need output will be like this: count 1 Media,,2 GB count 2 Document,,4 GB My problem is,... (16 Replies)
Discussion started by: sheikh76
16 Replies

5. Shell Programming and Scripting

The scripts not able to make the file to size 0, every times it go back to its original size

#!/bin/sh ########################################################################################################## #This script is being used for AOK application for cleaning up the .out files and zip it under logs directory. # IBM # Created #For pdocap201/pdoca202 .out files for AOK #1.... (0 Replies)
Discussion started by: mridul10_crj
0 Replies

6. Programming

CHAR Array - stuffed with values - with more size than it holds

Hi All I am simulating a problem in the production where i faced a situation. Please find the following example program which i simulated. #include<stdio.h> #include<stdlib.h> #include<string.h> int main() { char str1; (3 Replies)
Discussion started by: dhanamurthy
3 Replies

7. Programming

size of char array in c

i have to store a data more than 100000. i don't know the size of the data whether it may be 100000 or 1000000. so how can i define variable size; example char abc; but i don't know the size so how can i give array size?? in one sentence how can i give the array size dynamically so that i... (6 Replies)
Discussion started by: phani_sree
6 Replies

8. Solaris

command to find out total size of a specific file size (spread over the server)

hi all, in my server there are some specific application files which are spread through out the server... these are spread in folders..sub-folders..chid folders... please help me, how can i find the total size of these specific files in the server... (3 Replies)
Discussion started by: abhinov
3 Replies

9. Shell Programming and Scripting

Size of an array in sh shell script

Is there a way to find out the size of an array in sh shell script? Thanks. (1 Reply)
Discussion started by: trivektor
1 Replies

10. UNIX for Advanced & Expert Users

MAX SIZE ARRAY Can Hold it

Hi, Do anyone know what's the max size of array (in awk) can be store before hit any memory issue. Regards (3 Replies)
Discussion started by: epall
3 Replies

Featured Tech Videos