#Name

readlink - get symlink target

#Synopsis

#include <unistd.h>

ssize_t readlink(const char* path, char* buffer, size_t size)

#Description

readlink() writes up to size bytes of the target path of a symbolic link at the specified path to the given buffer. readlink() does not null-terminate the buffer. If the target of the link is longer than size bytes, it will get truncated.

#Return value

On success, readlink() returns the number of bytes written to the buffer, which is always less or equal to the specified size. Otherwise, it returns -1 and sets errno to describe the error.

#Notes

The underlying system call always returns the full size of the target path on success, not the number of bytes written. FileSystem::read_link() makes use of this to provide an alternative way to read links that doesn't require the caller to pick a buffer size and allocate a buffer straight up.

Since it's essentially impossible to guess the right buffer size for reading links, it's strongly recommended that everything uses FileSystem::read_link() instead.

#Examples

The following example demonstrates how one could implement an alternative version of getpid(2) which reads the calling process ID from ProcFS:

#include <LibFileSystem/FileSystem.h>
#include <unistd.h>

pid_t read_pid_using_readlink()
{
    char buffer[64];
    int rc = readlink("/proc/self", buffer, sizeof(buffer) - 1);
    if (rc < 0)
        return rc;
    buffer[rc] = 0;
    return atoi(buffer);
}

ErrorOr<pid_t> read_pid_using_core_file()
{
    auto target = TRY(FileSystem::read_link("/proc/self"sv));
    auto pid = target.to_number<pid_t>();
    VERIFY(pid.has_value());
    return pid.value();
}

#See also

• readlink(1)