could someone please, show me how to make a hard link to a file in c language ?
i am using minix. The program below reads the last number from file numbers, adds a one to it and then appends the new number into the file. I use a c script as driver to this program, the c script has 6 processors of this program. the processors read and write into the numbers file at the same time, causing disoder in the numbers file. so in order to put some order into this chaos, i want to use a hard link to the file numbers, which will prevent other processors to access the file when it is being used by onother processor.
But the way i am using link isn't working, can someone help ?
I am sorry for the lack of documentation in the code
Code:
# include <stdio.h>
# include <unistd.h>
int readlastline(void){
FILE *f_ptr = fopen("numbers", "r");
int last = 0;
fseek(f_ptr, -5, SEEK_END);
fscanf(f_ptr, "%5d", &last);
fclose(f_ptr);
return last;
}
void add_append(int i){
FILE *fp = fopen("numbers", "a");
if(i == 0){
fprintf(fp," %5d \n", i);
i++;
fprintf(fp," %5d \n", i);
}
else{
i++;
fprintf(fp," %5d \n", i);
}
fclose(fp);
}
void main(void){
int count = 0;
char *numbers = "numbers";
char *lock = "lock";
int x;
while ( count < 500){
count++;
if(link(numbers, lock) == 0){
printf("in %s \n", " link succeed ");
x = readlastline();
add_append(x);
unlink(lock);
}
}
}
--------------------------------------------------------------------------
The c script:
Code:
/bin/sh
# testcount1 drives multiple instances of count1
rm -f numbers # first remove the numbers file
echo 0 > numbers # and initialise it to contain a 0
./count3 & # run multiple processes in the background
./count3 &
./count3 &
./count3 &
./count3 &
./count3 # except for the last to let us know when they are done
# run ps to be certain all the processes have finished
Last edited by surubi_abada; 03-04-2010 at 02:22 PM..
I created a file named as file and a its hard link named as hlink.
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But as far as I think we cannot delete the file unless we delete all the hard links pointing to it.
Is there anything worng... (1 Reply)
Hello,
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Regards
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Hi
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