What is the LD_PRELOAD trick?

c linux environment-variables
Hank Gay picture Hank Gay · Jan 8, 2009 · Viewed 333.2k times · Source

I came across a reference to it recently on proggit and (as of now) it is not explained.

I suspect this might be it, but I don't know for sure.

Answer

JesperE picture JesperE · Jan 8, 2009

If you set LD_PRELOAD to the path of a shared object, that file will be loaded before any other library (including the C runtime, libc.so). So to run ls with your special malloc() implementation, do this:

$ LD_PRELOAD=/path/to/my/malloc.so /bin/ls

Related questions

Questions about putenv() and setenv()

I have been thinking a little about environment variables and have a few questions/observations. putenv(char *string); This call seems fatally flawed. Because it doesn't copy the passed string you can't call it with a local and there is …

Read More
Undefined reference to pthread_create in Linux

I picked up the following demo off the web from https://computing.llnl.gov/tutorials/pthreads/ #include <pthread.h> #include <stdio.h> #define NUM_THREADS 5 void *PrintHello(void *threadid) { long tid; tid = (long)threadid; printf("Hello …

Read More
Write to .txt file?

How can I write a little piece of text into a .txt file? I've been Googling for over 3-4 hours, but can't find out how to do it. fwrite(); has so many arguments, and I don't know how to use …

Read More