The getobjformat function queries several sources to determine the preferred object file format, and copies its name into a buffer provided by the caller.
The object file format is determined as follows. If argv is non- NULL and an explicit command line argument such as -aout or -elf is present, then that determines the object file format.
Otherwise, if the variable OBJFORMAT is set in the environment, the object file format is taken from its value.
Otherwise, if the file /etc/objformat is readable and contains a line of the form OBJFORMAT=xxx, the object file format is taken from there.
Otherwise, a built-in system default object file format is returned.
buf points to a user-supplied buffer into which the name of the object file format is copied. bufsize gives the size of the buffer in bytes. The string placed in buf is always null-terminated. It is an error if the buffer is too small to hold the null-terminated name.
argv points to a NULL -terminated argument vector to be scanned for object format options. argv may be NULL, in which case the argument vector is not scanned.
If argcp is non-NULL, any object format options are deleted from the argument vector, and the updated argument count is stored into the integer referenced by argcp. If argcp is NULL, the argument vector is left unchanged.
On success, getobjformat returns the length of the object file format name, not counting the null terminator. If the supplied buffer is too small to hold the object file format and its null terminator, getobjformat returns -1. In that case, the contents of the buffer and argument vector supplied by the caller are indeterminate.