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# fprintf

Input-Output Functions

Writes formatted output to a file.

    int fprintf( FILE *file_pointer, const char *format_string [, args ] );

file_pointer | A pointer to a file.
format_string | The formatted string to write to the file.
args | One or more optional print arguments.

## Return Values

On success, returns the Total number of characters printed. On error, returns a negative number.

For fprintf details, refer to your C language documentation.

## Example

The following example opens a log file and writes the id number and group name of the Virtual User to it using fprintf.

Copy code

        #include <stdio.h>
        #ifdef unix
            char * filename = "/tmp/logfile.txt";
        #else
            char * filename = "c:\\logfile.txt";
        #endif
        FILE* file;
        int id;
        char * groupname;
        // Create a new file
        if ((file = fopen(filename, "w" )) == NULL) {
            lr_output_message("Unable to create %s", filename);
            return -1;
        }
        // Write the Vuser ID and group to the log file
        lr_whoami(&id, &groupname, NULL);
        fprintf(file, "log file of virtual user ID: %d group: %s\n", id, groupname);
        fclose(file);

    Example: Written to log file:
    log file of virtual user ID: -1 group: None

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