fgetws_unlocked - Linux
Overview
fgetws_unlocked is a function used to read a line of text from a stream without locking the stream. It’s particularly useful for multithreaded applications where locking the stream for each read operation can cause performance issues.
Syntax
#include <stdio.h>
wchar_t *fgetws_unlocked(wchar_t * restrict s, int n, FILE * restrict stream);
- s: Pointer to the buffer where the read line will be stored.
- n: Maximum number of characters to read, including the terminating null character (
\0
). - stream: Pointer to the stream from which the line will be read.
Options/Flags
None.
Examples
Simple Usage:
#include <stdio.h>
int main() {
wchar_t buffer[1024];
FILE *stream = fopen("input.txt", "r");
if (stream) {
fgetws_unlocked(buffer, sizeof(buffer), stream);
printf("%ws", buffer);
fclose(stream);
}
return 0;
}
Complex Usage (Reading Lines from Multiple Streams in a Loop):
#include <stdio.h>
#include <pthread.h>
void *read_stream(void *arg) {
FILE *stream = (FILE *)arg;
wchar_t buffer[1024];
while (fgetws_unlocked(buffer, sizeof(buffer), stream)) {
// Process the line
}
return NULL;
}
int main() {
pthread_t thread1, thread2;
FILE *stream1 = fopen("input1.txt", "r");
FILE *stream2 = fopen("input2.txt", "r");
if (stream1 && stream2) {
pthread_create(&thread1, NULL, read_stream, stream1);
pthread_create(&thread2, NULL, read_stream, stream2);
pthread_join(thread1, NULL);
pthread_join(thread2, NULL);
fclose(stream1);
fclose(stream2);
}
return 0;
}
Common Issues
- Ensure that the buffer provided is large enough to hold the entire line.
- Check the return value to determine if the end of file was reached or an error occurred.
- Be cautious when using fgetws_unlocked in multithreaded environments, as the stream is not locked during the read operation.
Integration
fgetws_unlocked can be used in conjunction with other functions for advanced tasks, such as:
- getline: For reading lines of characters from a stream without the need to specify a buffer size.
- fgets: For reading lines of characters from a stream with locking.
Related Commands
- fgets
- getline
- scanf