.\" Copyright (c) 1998 John D. Polstra
.\" All rights reserved.
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.\" $FreeBSD: src/lib/libc/gen/getobjformat.3,v 1.8 2001/10/01 16:08:51 ru Exp $
.\"
.Dd September 7, 1998
.Dt GETOBJFORMAT 3
.Os
.Sh NAME
.Nm getobjformat
.Nd get preferred object file format
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In objformat.h
.Ft int
.Fn getobjformat "char *buf" "size_t bufsize" "int *argcp" "char **argv"
.Sh DESCRIPTION
.Fn getobjformat
queries several sources to determine the preferred object file
format, and copies its name into a buffer provided by the caller.
.Pp
The object file format is determined as follows.  If
.Va argv
is
.No non- Ns Ev NULL
and an explicit command line argument such as
.Fl aout
or
.Fl elf
is present, then that determines the object file format.
.Pp
Otherwise, if the variable
.Ev OBJFORMAT
is set in the environment, the object file format is taken from its
value.
.Pp
Otherwise, if the file
.Pa /etc/objformat
is readable and contains a line of the form
.Ql OBJFORMAT=xxx ,
the object file format is taken from there.
.Pp
Otherwise, a built-in system default object file format is returned.
.Pp
.Va buf
points to a user-supplied buffer into which the name of the object
file format is copied.
.Va bufsize
gives the size of the buffer in bytes.  The string placed in
.Va buf
is always null-terminated.  It is an error if the buffer is too
small to hold the null-terminated name.
.Pp
.Va argv
points to a
.Dv NULL Ns -terminated
argument vector to be scanned for object
format options.
.Va argv
may be
.Dv NULL ,
in which case the argument vector is not scanned.
.Pp
If
.Va 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
.Va argcp .
If
.Va argcp
is
.Dv NULL ,
the argument vector is left unchanged.
.Sh RETURN VALUES
On success,
.Fn 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,
.Fn getobjformat
returns -1.  In that case, the contents of the buffer and argument
vector supplied by the caller are indeterminate.
.Sh ENVIRONMENT
.Bl -tag -width OBJFORMAT
.It Ev OBJFORMAT
If the environment variable
.Ev OBJFORMAT
is set, it overrides the default object file format.
.Ev OBJFORMAT takes precedence over
.Pa /etc/objformat .
.El
.Sh FILES
.Bl -tag -width /etc/objformat -compact
.It Pa /etc/objformat
If present, specifies the object file format to use.  Syntax is
.Ql OBJFORMAT=xxx .
.El
.Sh SEE ALSO
.Xr objformat 1
.Sh HISTORY
The
.Fn getobjformat
function first appeared in
.Fx 3.0 .