d43a7eae54
As usual, this removes many unused includes and moves used includes further down the chain.
69 lines
1.8 KiB
Markdown
69 lines
1.8 KiB
Markdown
## Name
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readlink - get symlink target
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## Synopsis
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```**c++
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#include <unistd.h>
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ssize_t readlink(const char* path, char* buffer, size_t size)
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```
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## Description
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`readlink()` writes up to `size` bytes of the target path of a symbolic link at
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the specified `path` to the given `buffer`. `readlink()` does not
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null-terminate the buffer. If the target of the link is longer than `size`
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bytes, it will get truncated.
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## Return value
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On success, `readlink()` returns the number of bytes written to the buffer,
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which is always less or equal to the specified `size`. Otherwise, it returns -1
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and sets `errno` to describe the error.
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## Notes
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The underlying system call always returns the full size of the target path on
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success, not the number of bytes written. `Core::DeprecatedFile::read_link()` makes use
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of this to provide an alternative way to read links that doesn't require the
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caller to pick a buffer size and allocate a buffer straight up.
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Since it's essentially impossible to guess the right buffer size for reading
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links, it's strongly recommended that everything uses `Core::DeprecatedFile::read_link()`
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instead.
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## Examples
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The following example demonstrates how one could implement an alternative
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version of `getpid(2)` which reads the calling process ID from ProcFS:
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```c++
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#include <LibCore/DeprecatedFile.h>
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#include <unistd.h>
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pid_t read_pid_using_readlink()
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{
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char buffer[64];
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int rc = readlink("/proc/self", buffer, sizeof(buffer) - 1);
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if (rc < 0)
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return rc;
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buffer[rc] = 0;
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return atoi(buffer);
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}
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pid_t read_pid_using_core_file()
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{
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auto target = Core::DeprecatedFile::read_link("/proc/self");
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if (target.is_null())
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return -1;
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auto pid = target.to_uint();
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ASSERT(pid.has_value());
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return pid.value();
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}
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```
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## See also
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* [`readlink`(1)](help://man/1/readlink)
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