Linux Learning Notes System standard: Posix,iso C ...

First, Posix,iso c,single the concept of UNIX specification.

1,posix:portable Operating System Interface. Portable operating System interface. expect to obtain source-level software portability.

2,iso C: Provides standardization of C language. Improve the portability of C languages on different operating systems. It defines the syntax, semantics, and standard libraries of the C language.

3,single a superset of the UNIX specification:posix.1 standard , defines additional interfaces that extend the functionality of the basic POSIX.1 specification. The complete collection of the corresponding system interfaces is known as the X/open system interface (Xsi,x/open systems Interface).

4:posix obey the ISO C standard: That is, when the conflict arises, the ISO C shall prevail. Also, pay attention to the units of return values (frequency, microseconds, seconds, etc.) between each standard.

Second, the sysconf,pathconf,fpathconf:posix specifies the operating system of the various restrictions (such as the maximum number of files), these 3 functions can be at run time to obtain a specific limit value.

1,sysconf: Get options unrelated to file/directory.

2,pathconf: Options related to files/directories. (use path as parameter)

3:fpathconf: Options related to files/directories. (use file descriptors as parameters)

4: You can improve the portability of your programs by using these functions.

4: These functions detect limit values only at run time. You can find the limit values in the "unistd.h" header file at compile time.

Linux Learning Notes System standard: Posix,iso C ...