This table shows some example precision format strings. When skip is specified, fread reads in at most a repetition factor number of values default is 1does a skip of input specified by the skip argument, reads in another block of values, does a skip of input, and so on, until size number of values have beenread. If precision is a bit format like 'bitN' or 'ubitN', skip is specified in bits.
It accepts the same arguments as fwrite function does. The function reads n items from the file where each item occupies the number of bytes specified in the second argument.
On success, it reads n items from the file and returns n. On error or end of the file, it returns a number less than n.
Let's take some examples: Reading an array from the file int arr; fread arr, sizeof arr1, fp ; This reads an array of 10 integers from the file and stores it in the variable arr. Reading the first 5 elements of an array int arr; fread arr, sizeof int5, fp ; This reads 5 integers from the file and stores it in the variable arr.
The following program demonstrates how we can use fread function. The structure employee has four members namely: In line 14, a structure pointer fp of type struct FILE is declared.
In line 15, fopen function is called with two arguments namely "employee. On success, it returns a pointer to file employee. On failure, it returns NULL. In linesif statement is used to test the value of fp. If it is NULL, printf statement prints the error message and program terminates.
Otherwise, the program continues with the statement following the if statement. In linesa while loop is used along with fread to read the contents of the file.
The fread function reads the records stored in the file one by one and stores it in the structure variable emp.
The fread function will keep returning 1 until there are records in the file. As soon as the end of the file is encountered fread will return a value less than 1 and the condition in the while loop become false and the control comes out of the while loop.
In line 33, fclose function is used to close the file.After having problems with fwrite() returning 0 in cases where one would fully expect a return value of false, I took a look at the source code for php's fwrite() itself. The function will only return false if you pass in invalid arguments.
The values are extracted in column-major order. The remaining arguments precision, skip, and arch are optional, and are interpreted as described for fread.
The behavior of fwrite is undefined if the values in data are too large to fit in the specified precision. I know the values in the vector are correct, because a) if I comment out the "fixed" flag it works, and b) one of the unsigned vectors is sorted based on the values in that double vector (after it is printed, so the sort cannot corrupt the vector print) and works perfectly.
The fread() function returns the number of items read. The feof function should be used to detect end-of-file if fread returns 0. feof returns a non-zero value when EOF has previously been detected reading the named input stream.
It returns 0 otherwise. See the permissions parameter to the fopen function. When opening a file in text mode on Windows, the sequence \r\n (13,10) is replaced with \n (10). This happens before fread gets to it.
If fwrite is non-null, select will return immediately if there is a UDP socket in the fwrite list, or when any TCP socket in the fwrite list which is not a non-blocking socket is .