explain_setenv(3) Library Functions Manual explain_setenv(3)
NAME
explain_setenv - explain setenv(3) errors
SYNOPSIS
#include <libexplain/setenv.h>
const char *explain_setenv(const char *name, const char *value, int overwrite);
const char *explain_errno_setenv(int errnum, const char *name, const char *value, int overwrite);
void explain_message_setenv(char *message, int message_size, const char *name, const char *value, int overwrite);
void explain_message_errno_setenv(char *message, int message_size, int errnum, const char *name, const char *value, int overwrite);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the setenv(3) system call.
explain_setenv
const char *explain_setenv(const char *name, const char *value, int overwrite);
The explain_setenv function is used to obtain an explanation of an error returned by the setenv(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.
name The original name, exactly as passed to the setenv(3) system call.
value The original value, exactly as passed to the setenv(3) system call.
overwrite
The original overwrite, exactly as passed to the setenv(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.
Example: This function is intended to be used in a fashion similar to the following example:
if (setenv(name, value, overwrite) < 0)
{
fprintf(stderr, "%s
", explain_setenv(name, value, overwrite));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setenv_or_die(3) function.
explain_errno_setenv
const char *explain_errno_setenv(int errnum, const char *name, const char *value, int overwrite);
The explain_errno_setenv function is used to obtain an explanation of an error returned by the setenv(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.
errnum The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is neces-
sary 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.
name The original name, exactly as passed to the setenv(3) system call.
value The original value, exactly as passed to the setenv(3) system call.
overwrite
The original overwrite, exactly as passed to the setenv(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.
Example: This function is intended to be used in a fashion similar to the following example:
if (setenv(name, value, overwrite) < 0)
{
int err = errno;
fprintf(stderr, "%s
", explain_errno_setenv(err, name, value, overwrite));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setenv_or_die(3) function.
explain_message_setenv
void explain_message_setenv(char *message, int message_size, const char *name, const char *value, int overwrite);
The explain_message_setenv function is used to obtain an explanation of an error returned by the setenv(3) system call. The least the mes-
sage 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.
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.
name The original name, exactly as passed to the setenv(3) system call.
value The original value, exactly as passed to the setenv(3) system call.
overwrite
The original overwrite, exactly as passed to the setenv(3) system call.
Example: This function is intended to be used in a fashion similar to the following example:
if (setenv(name, value, overwrite) < 0)
{
char message[3000];
explain_message_setenv(message, sizeof(message), name, value, overwrite);
fprintf(stderr, "%s
", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setenv_or_die(3) function.
explain_message_errno_setenv
void explain_message_errno_setenv(char *message, int message_size, int errnum, const char *name, const char *value, int overwrite);
The explain_message_errno_setenv function is used to obtain an explanation of an error returned by the setenv(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.
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 neces-
sary 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.
name The original name, exactly as passed to the setenv(3) system call.
value The original value, exactly as passed to the setenv(3) system call.
overwrite
The original overwrite, exactly as passed to the setenv(3) system call.
Example: This function is intended to be used in a fashion similar to the following example:
if (setenv(name, value, overwrite) < 0)
{
int err = errno;
char message[3000];
explain_message_errno_setenv(message, sizeof(message), err, name, value, overwrite);
fprintf(stderr, "%s
", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_setenv_or_die(3) function.
SEE ALSO
setenv(3)
change or add an environment variable
explain_setenv_or_die(3)
change or add an environment variable and report errors
COPYRIGHT
libexplain version 0.52
Copyright (C) 2010 Peter Miller
explain_setenv(3)