How to Check Directory Existence in Unix Using System Calls?
Nov 07, 2024 pm 01:09 PMChecking Directory Existence in Unix: A Comprehensive Guide Using System Calls
Problem:
In Unix, how can one determine the existence of a directory using a system call without opening it or handling related errors?
Answer:
POSIX systems provide two essential functions for this purpose: stat() and lstat(). These functions allow you to ascertain whether a pathname reflects a valid accessible object and retrieve information about its type.
Key Differences Between stat() and lstat():
- stat(): Follows symbolic links and provides information about the final destination.
- lstat(): Provides information about the symbolic link itself, regardless of any targets it may point to.
Implementation Using stat():
#include <sys/stat.h> struct stat sb; if (stat(pathname, &sb) == 0 && S_ISDIR(sb.st_mode)) { // True if pathname is a directory }
Additional File Type Verification:
Using the S_IS* macros from
- S_ISREG: Regular file
- S_ISCHR: Character device
- S_ISBLK: Block device
- S_ISFIFO: FIFO
- S_ISLNK: Symbolic link
- S_ISSOCK: Socket
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