What are the library functions in the C language?

The library functions in the C language include:

1. Standard input and output library functions include printf, scanf, getchar, putchar, and so on.
2. Library functions for string manipulation: strlen, strcpy, strcat, strcmp, etc.
3. Memory management library functions such as malloc, calloc, realloc, and free.
4. Library functions for file operations: fopen, fclose, fread, fwrite, etc.
5. Mathematical library functions such as sqrt, sin, cos, and abs.
6. Library functions for working with date and time: time, ctime, gmtime, strftime, etc.
7. Dynamic link library functions such as dlopen, dlsym, and dlclose.
8. Network communication library functions such as socket, bind, listen, accept, etc.
9. Multithreading library functions such as pthread_create, pthread_join, pthread_mutex_init, etc.
10. Graphic interface library functions: functions related to operations on windows, buttons, text boxes, etc.

The above only lists some commonly used C library functions, in reality, the C library functions are very extensive, and you can search for relevant functions based on specific needs.