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× C++ Standard Library C++ STL Library


The C++ <cstdio> fgets() function reads at most (num-1) characters from the given stream and stores them as a C string into str. Parsing stops if a newline character is found, in which case str will contain that newline character, or the end-of-file is reached.

A terminating null character is automatically appended after the characters copied to str.

Syntax

char * fgets ( char * str, int num, FILE * stream );

Parameters

str Specify pointer to an array of chars where the string read is copied.
num Specify maximum number of characters to be copied into str.
stream Specify a pointer to a FILE object that specifies an input stream.

Return Value

  • On success, str is returned, On failure, null pointer is returned.
  • If the failure has been caused due to end-of-file condition, additionally sets the end-of-file indicator feof() on stream. If this happens before any characters could be read, in which case a null pointer is returned and the contents of str remains unchanged.
  • If error occurs due to some other reason, additionally sets the error indicator ferror() on stream.

Example:

Lets assume that we have a file called test.txt. This file contains following content:

This is a test file.

In the below example, file is opened using fopen() function in read mode. It reads first 9 characters from the file and prints them on screen.

#include <cstdio>
 
int main (){
  //open the file in read mode
  FILE *pFile = fopen("test.txt", "r");
  char mystring [10];

  //read first 9 characters from the file
  if(fgets(mystring, 10, pFile) != NULL)
    puts(mystring);
  
  //close the file
  fclose(pFile);
  return 0;
}

The output of the above code will be:

This is a

❮ C++ <cstdio> Library

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