fprintf - Formatted output to a file

Definition	#include <stdio.h> int fprintf(FILE *fp, const char *format, argumentlist); fprintf edits data (characters, strings, numeric values) according to the specifications in the format string and writes this data to the file with file pointer fp. fprintf works like printf, except that the edited data is written to a file and not to the standard output.
Parameters	FILE *fp File pointer to the output file. const char *format Format string as described under printf with KR or ANSI functionality (see printf). argumentlist Variables or constants whose values are to be converted and formatted for output according to the information in the format statements. If the number of format statements does not match the number of arguments the following applies: If there are more arguments, the surplus arguments are ignored. If there are fewer arguments, the results are undefined.
Return val.	number of characters output if successful. Negative value if an error occurs.
Notes	fprintf rounds to the specified precision when converting floating-point numbers. fprintf does not convert one data type to another. A value must be explicitly converted (e.g. with the cast operator) if it is not to be output to conformity with its type. The characters are not written immediately to the external file but are stored in an internal C buffer (see section “Buffering” (Basic terms)). Maximum number of characters to be output With KR functionality (applies to C/C++ versions prior to V3.0 only) a maximum of 1400 characters can be output per fprintf call, with ANSI functionality a maximum of 1400 characters per conversion element (e.g. %s). Attempts to output non-initialized variables or to output variables in a manner inconsistent with their data type can lead to undefined results. The behavior is undefined if the percent sign (%) in a format statement is followed by an undefined formatting or conversion character. The following applies in the case of text files with SAM access mode and variable record length for which a maximum record length is also specified: When the specification split=no was entered for fopen, records which are longer than the maximum record length are truncated to the maximum record length when they are written. By default or with the specification split=yes, these records are split into multiple records. If a record has precisely the maximum record length, a record of the length zero is written after it.
Example	#include <stdio.h> #include <stdlib.h> int main(void) { FILE *fp; char c, name[40]; int i; char *string; double d; printf("Name of the output file: \n"); gets(name); if((fp = fopen(name,"w")) == NULL) { printf("Can't open %s\n", name); exit(1); } c = 'A'; i = 999; string = "This is a string.";    d = 123.456; fprintf(fp, "%c %d %s %f\n", c, i, string, d); fclose(fp); puts("Correct output to file:A 999 This is a string. 123.456000"); return 0; }
See also	printf, sprintf, snprintf, putc, putchar, puts, scanf, fscanf