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

# explain\_fork(3)

explain fork(2) errors

## NAME

explain\_fork - explain [fork(2)](/fork/2.md) errors

## SYNOPSIS

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

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

## DESCRIPTION

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

### explain\_fork

const char \*explain\_fork(void);

The **explain\_fork** function is used to obtain an explanation of an error returned by the [*fork*(2)](/fork/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 (fork() < 0)
{
    fprintf(stderr, "%s\n", explain_fork());
    exit(EXIT_FAILURE);
}
```

- 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\_fork

const char \*explain\_errno\_fork(int errnum);

The **explain\_errno\_fork** function is used to obtain an explanation of an error returned by the [*fork*(2)](/fork/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 (fork() < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_fork(err, ));
    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*.

- 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\_fork

void explain\_message\_fork(char \*message, int message\_size);

The **explain\_message\_fork** function may be used to  obtain an explanation of an error returned by the [*fork*(2)](/fork/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 (fork() < 0)
{
    char message[3000];
    explain_message_fork(message, sizeof(message), );
    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.

### explain\_message\_errno\_fork

void explain\_message\_errno\_fork(char \*message, int message\_size, int errnum);

The **explain\_message\_errno\_fork** function may be used to obtain an explanation of an error returned by the [*fork*(2)](/fork/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 (fork() < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_fork(message, sizeof(message), err, );
    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*.

## SEE ALSO

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

  create a child process

- [*explain\_fork\_or\_die*(3)](/explain_fork_or_die/3.md)

  create a child process and report errors

## COPYRIGHT

libexplain version 1.4\
 Copyright (C) 2008 Peter Miller