Advanced Programming in the UNIX® Environment

ptg10805159

96 Files and Directories Chapter 4

MacroType of file

S_ISREG() regular file

S_ISDIR() directory file

S_ISCHR() character special file

S_ISBLK() block special file

S_ISFIFO() pipe or FIFO

S_ISLNK() symbolic link

S_ISSOCK() socket

Figure 4.1 File type macros in<sys/stat.h>

POSIX.1 allows implementations to represent interprocess communication(IPC)

objects, such as message queues and semaphores, as files. The macros shown in

Figure4.2 allow us to determine the type of IPC object from thestatstructure. Instead

of taking thest_modemember as an argument, these macros differ from those in

Figure4.1 in that their argument is a pointer to thestatstructure.

MacroType of object

S_TYPEISMQ() message queue

S_TYPEISSEM() semaphore

S_TYPEISSHM() shared memory object

Figure 4.2 IPC type macros in<sys/stat.h>

Message queues, semaphores, and shared memory objects arediscussed in Chapter 15.

However,none of the various implementations of the UNIX System discussed in this

book represent these objects as files.

Example

The program in Figure4.3 prints the type of file for each command-line argument.

#include "apue.h"

int

main(int argc, char *argv[])

{

int i;

struct stat buf;

char *ptr;

for (i = 1; i < argc; i++) {

printf("%s: ", argv[i]);

if (lstat(argv[i], &buf) < 0) {

err_ret("lstat error");

continue;

}

if (S_ISREG(buf.st_mode))

ptr = "regular";

else if (S_ISDIR(buf.st_mode))