CODEWITHSUNDEEP
csymlink
Ralph
Ralph

Reputation: 6399

following symbolic links in C

I'm looking to write a C program which, given the name of symbolic link, will print the name of the file or directory the link points to. Any suggestions on how to start?

Upvotes: 10

Views: 18780

Answers (4)

Jonathan Leffler
Jonathan Leffler

Reputation: 753695

The readlink() function that has been mentioned is part of the answer. However, you should be aware of its horrid interface (it does not null terminate the response string!).

You might also want to look at the realpath() function, the use of which was discussed in SO 1563186. You could also look at the code for 'linkpath' at the IIUG Software Archive. It analyzes the security of all the directories encountered as a symbolic link is resolved - it uses readlink() and lstat() and stat(); one of the checks when testing the program was to ensure that realpath() resolved the name to the same file.

Upvotes: 11

Andy Ross
Andy Ross

Reputation: 12043

The system call you want is readlink(). Takes a path to the link, returns the string (not always a valid path in the filesystem!) stored in the link. Check the man page ("man 2 readlink") for details.

Note there is some ambiguity to your question. You might be asking for how to tell the "real" path in the filesystem, which is a little more complicated.

Upvotes: 1

Tim
Tim

Reputation: 9259

Make sure that you have an environment which supports POSIX functions, include unistd.h and then use the readlink function.

Upvotes: 9

the_mandrill
the_mandrill

Reputation: 30842

Depending on the platform, stat() or fstat() are probably the first things to try out. If you're on Linux or cygwin then the stat program will give you a reasonable idea of what to expect from the system API call (it pretty much gives you a text dump of it).

Upvotes: 1

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