Tag Archives: open file

Job Interview question: How to stream output, open file, and read file in C++ and C

Job Interview question: How to stream output, open file, and read file in C++ and C

To stream to clog, set:
#include
#include

void main ( )
{
using namespace std;

// open the file “file_name.txt”
// for reading
ifstream in(“file_name.txt”);

// output the all file to stdout
if ( in )
cout << in.rdbuf(); else // if the ifstream object is in a bad state // output an error message to stderr clog << "Error while opening the file" << endl; } How to open and read a file: #include

void readone();

int main(int argn, char **argv)
{
int i;
for (i=0; i<=2; i++){ readone(); } } void readone() { static int ctr = 0; FILE *f = fopen("test.txt", "r"); char str[100]; int i; for (i=0; i<=ctr; i++){ fscanf(f, "%[^\n]\n", str); } puts(str); fclose(f); ctr++; } Beaware of ftell and fseek: /* ftell example : getting size of a file */ #include

int main ()
{
FILE * pFile;
long size;

pFile = fopen (“myfile.txt”,”rb”);
if (pFile==NULL) perror (“Error opening file”);
else
{
fseek (pFile, 0, SEEK_END);
size=ftell (pFile);
fclose (pFile);
printf (“Size of myfile.txt: %ld bytes.\n”,size);
}
return 0;
}

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