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• #2084
Ms.R
Participant

I am new to C, literally. My lovely professor wants us to teach ourselves to program while he compiles it and tells us we’re wrong without going into any details. If it compiles and it runs = A, if it doesn’t = F. There’s no inbetween. By the way, this is to be compiled using “gcc” in an UNIX environment

part a:
First of all, you are supposed to write a program in either C or C++ that reads data from a file and copies it to another file. Your program should copy all contents of the file.

part b:
Secondly, write another program to create child processes from your main program recursively using fork( ) and exec( ) commands up to a certain level, for example, fifth level. Then print identification of each child process in each level.

My code:
Part A:Code:

#include
#include
int main(void)
{
// open a text file for reading
FILE *in_file
in_file = fopen("input.txt","r");

// open a text file for writing
FILE *out_file
out_file = fopen("output.txt","w");

if(!f)
{ return 1; }

while(fgets(s,80,in_file) != NULL)
{
//write to file
fprintf(out_file, "%s",s");
fprintf(out_file, "n");
}

fclose(in_file);
fclose(out_file);
system("pause");
return 0;
}

Part B:Code:

#include
#include

int main()
{
/* call the recursive function */
recurse(5);
}

void recurse(int count)
{
Pid_t pid;
pid = fork();

if(pid < 0)
{
/* if the fork failed give error */
fprintf(stderr, "Fork Failed");
exit(-1);
}

else if (pid == 0)
{
/* child process and print the ID*/
execlp("/bin/ls", "ls", NULL);
printf("Child Process ID: " + pid);
}

else
{
/* parent process */
/* parent will wait for the child to complete */
wait (NULL);
exit(0);
}

/* if the count is less than one, we're finished */
if(count > 1)
{
exit(0);
}

/* decrement count and call itself (recursion) */
else
{
count = count - 1;
recurse(count - 1)
}
}


Please helpe me?!!?! What am I doing wrong? What am I missing? This guy told me it’d be easy because I “know” Java and it isn’t. I honestly think learning Ada was a lot easier than C.

• #3370
Humayan
Participant

For the first part you could do:

#include
#include
int main(void)
{
// open a text file for reading
FILE * in_file;
in_file = fopen("c:\programs\help\text1.txt","r");
// open a text file for writing
FILE * out_file ;
out_file = fopen("c:\programs\help\text2.txt","w");

if ( ! in_file || ! out_file )
{
printf ( "a file did not openn" );
return 1;
}
char ch = fgetc ( in_file );
while ( ch != EOF )
{
//write to file
fputc ( ch , out_file );
ch = fgetc ( in_file );
}
fclose(in_file);
fclose(out_file);
// system("pause");
return 0;
}