CODEWITHSUNDEEP
cexecve
SdFRO0QS78
SdFRO0QS78

Reputation: 91

Can't pass 2nd environment variable with execve

I would like to display 2 environment variables that are passed as argument to another process using execve() function:

Main.c:

int main(){


    char USERNAME[10];
    strcpy(USERNAME, "USERNAME=");
    for (int i=1;i<10;i++){
        strcpy(USERNAME+i, "1");
    }

    char PATH[169];
    strcpy(PATH, "PATH=");
    for (int i=5;i<169;i++){
        strcpy(PATH+i, "A");
    }


    char * newargv[] = {"./get","", (char*)0};
    char * newenviron[] = {PATH,USERNAME};
    execve("./get", newargv, newenviron);
    return 0;
}

get.c:

int main()
{
    const char* s = getenv("PATH");
    printf("PATH :%s\n",s);
    const char* s2 = getenv("USERNAME");
    printf("USERNAME :%s\n",s2);
}

So I compile Main.c to Main and get.c to get, and execute Main, I get this output:

PATH :AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA USERNAME :(null)

I don't understand why USERNAME is NULL here.

Upvotes: 0

Views: 258

Answers (2)

SdFRO0QS78
SdFRO0QS78

Reputation: 91

Oups my bad, I erased the "USERNAME=" part of the USERNAME tab, because loop started from 1 instead of 9...

Upvotes: 0

Joseph Sible-Reinstate Monica
Joseph Sible-Reinstate Monica

Reputation: 48672

You're missing a null terminator on the end of your newenviron array. Also, you're writing one more byte to each string than you've allocated space for (the ending \0 counts as a character).

Upvotes: 2

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