mirror of
https://github.com/RGBCube/serenity
synced 2025-10-31 12:12:45 +00:00
98c0c5e9e6
The URLs of the form `help://man/<section>/<page>` link to another help page inside the help application. All previous relative page links are replaced by this new form. This doesn't change any behavior but it looks much nicer :^) Note that man doesn't handle these new links, but the previous relative links didn't work either.
69 lines
1.8 KiB
Markdown
69 lines
1.8 KiB
Markdown
## Name
|
|
|
|
readlink - get symlink target
|
|
|
|
## Synopsis
|
|
|
|
```**c++
|
|
#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. `Core::File::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 `Core::File::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:
|
|
|
|
```c++
|
|
#include <LibCore/File.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);
|
|
}
|
|
|
|
pid_t read_pid_using_core_file()
|
|
{
|
|
auto target = Core::File::read_link("/proc/self");
|
|
if (target.is_null())
|
|
return -1;
|
|
auto pid = target.to_uint();
|
|
ASSERT(pid.has_value());
|
|
return pid.value();
|
|
}
|
|
```
|
|
|
|
## See also
|
|
|
|
* [`readlink`(1)](help://man/1/readlink)
|