explain_system

const char *explain_system(const char *command);

The explain_system function is used to obtain an explanation of an error returned by the system(3) 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 (system(command) < 0)
{


    fprintf(stderr, "%s\n", explain_system(command));


    exit(EXIT_FAILURE);
}

command

The original command, exactly as passed to the system(3) 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_system

const char *explain_errno_system(int errnum, const char *command);

The explain_errno_system function is used to obtain an explanation of an error returned by the system(3) 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 (system(command) < 0)
{


    int err = errno;


    fprintf(stderr, "%s\n", explain_errno_system(err, command));


    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.

command

The original command, exactly as passed to the system(3) 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_system

void explain_message_system(char *message, int message_size, const char *command);

The explain_message_system function may be used to obtain an explanation of an error returned by the system(3) 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 (system(command) < 0)
{


    char message[3000];


    explain_message_system(message, sizeof(message), command);


    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.

command

The original command, exactly as passed to the system(3) system call.

explain_message_errno_system

void explain_message_errno_system(char *message, int message_size, int errnum, const char *command);

The explain_message_errno_system function may be used to obtain an explanation of an error returned by the system(3) 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 (system(command) < 0)
{


    int err = errno;


    char message[3000];


    explain_message_errno_system(message, sizeof(message), err, command);


    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.

command

The original command, exactly as passed to the system(3) system call.