---
name: "explain_link"
section: "3"
platform: "linux"
package: "libexplain-dev"
version: "1.4.D001-16"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/explain_link"
---

# explain\_link(3)

explain link(2) errors

## NAME

explain\_link - explain [link(2)](/link/2.md) errors

## SYNOPSIS

\#include \<libexplain/link.h\>

const char \*explain\_link(const char \*oldpath, const char \*newpath);\
 const char \*explain\_errno\_link(int errnum, const char \*oldpath, const char \*newpath);\
 void explain\_message\_link(char \*message, int message\_size, const char \*oldpath, const char \*newpath);\
 void explain\_message\_errno\_link(char \*message, int message\_size, int errnum, const char \*oldpath, const char \*newpath);

## DESCRIPTION

These functions may be used to obtain explanations for errors returned by the [*link*(2)](/link/2.md) system call.

### explain\_link

const char \*explain\_link(const char \*oldpath, const char \*newpath);

The **explain\_link** function is used to obtain an explanation of an error returned by the [*link*(2)](/link/2.md) system call.  The least the message will contain is the value of `strerror(errno)`, but usually it will do much better, and indicate the underlying cause in more detail.

The *errno* global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:

```
if (link(oldpath, newpath) < 0)
{
    fprintf(stderr, "%s\n", explain_link(oldpath, newpath));
    exit(EXIT_FAILURE);
}
```

- *oldpath*

  The original oldpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- *newpath*

  The original newpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- Returns:

  The message explaining the error.  This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list.  This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

**Note:** This function is **not** thread safe, because it shares a return buffer across all threads, and many other functions in this library.

### explain\_errno\_link

const char \*explain\_errno\_link(int errnum, const char \*oldpath, const char \*newpath);

The **explain\_errno\_link** function is used to obtain an explanation of an error returned by the [*link*(2)](/link/2.md) system call. The least the message will contain is the value of `strerror(errnum)`, but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:

```
if (link(oldpath, newpath) < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_link(err, oldpath, newpath));
    exit(EXIT_FAILURE);
}
```

- *errnum*

  The error value to be decoded, usually obtained from the *errno* global variable just before this function is called.  This is necessary if you need to call **any** code between the system call to be explained and this function, because many libc functions will alter the value of *errno*.

- *oldpath*

  The original oldpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- *newpath*

  The original newpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- Returns:

  The message explaining the error.  This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list.  This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

**Note:** This function is **not** thread safe, because it shares a return buffer across all threads, and many other functions in this library.

### explain\_message\_link

void explain\_message\_link(char \*message, int message\_size, const char \*oldpath, const char \*newpath);

The **explain\_message\_link** function may be used to  obtain an explanation of an error returned by the [*link*(2)](/link/2.md) system call. The least the message will contain is the value of `strerror(errno)`, but usually it will do much better, and indicate the underlying cause in more detail.

The *errno* global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:

```
if (link(oldpath, newpath) < 0)
{
    char message[3000];
    explain_message_link(message, sizeof(message), oldpath, newpath);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
```

- *message*

  The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

- *message\_size*

  The size in bytes of the location in which to store the returned message.

- *oldpath*

  The original oldpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- *newpath*

  The original newpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

### explain\_message\_errno\_link

void explain\_message\_errno\_link(char \*message, int message\_size, int errnum, const char \*oldpath, const char \*newpath);

The **explain\_message\_errno\_link** function may be used to obtain an explanation of an error returned by the [*link*(2)](/link/2.md) system call. The least the message will contain is the value of `strerror(errnum)`, but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:

```
if (link(oldpath, newpath) < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_link(message, sizeof(message), err,
        oldpath, newpath);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
```

- *message*

  The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.

- *message\_size*

  The size in bytes of the location in which to store the returned message.

- *errnum*

  The error value to be decoded, usually obtained from the *errno* global variable just before this function is called.  This is necessary if you need to call **any** code between the system call to be explained and this function, because many libc functions will alter the value of *errno*.

- *oldpath*

  The original oldpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

- *newpath*

  The original newpath, exactly as passed to the [*link*(2)](/link/2.md) system call.

## SEE ALSO

- [*link*(2)](/link/2.md)

  make a new name for a file

- [*explain\_link\_or\_die*(3)](/explain_link_or_die/3.md)

  make a new name for a file and report errors

## COPYRIGHT

libexplain version 1.4\
 Copyright (C) 2008 Peter Miller