confstr.3

早期freebsd实现

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.\"	@(#)confstr.3	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt CONFSTR 3
.Os BSD 4
.Sh NAME
.Nm confstr
.Nd get string-valued configurable variables
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft size_t
.Fn confstr "int name" "char *buf" "size_t len"
.Sh DESCRIPTION
.Bf -symbolic
This interface is obsoleted by sysctl(3).
.Ef
.Pp
The
.Fn confstr
function provides a method for applications to get configuration
defined string values.
.Pp
The
.Fa name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
.Li <unistd.h> .
The
.Fa len
argument specifies the size of the buffer referenced by the
argument
.Fa buf .
If
.Fa len
is non-zero,
.Fa buf
is a non-null pointer, and
.Fa name
has a value, up to
.Fa len
\- 1 bytes of the value are copied into the buffer 
.Fa buf .
The copied value is always null terminated.
.Pp
The available values are as follows:
.Pp
.Bl -tag -width "123456"
.Pp
.It Li _CS_PATH
Return a value for the
.Ev PATH
environment variable that finds all the standard utilities.
.El
.Sh RETURN VALUES
If the call to
.Nm confstr
is not successful, \-1 is returned and
.Va errno
is set appropriately.
Otherwise, if the variable does not have a configuration defined value,
0 is returned and
.Va errno
is not modified.
Otherwise, the buffer size needed to hold the entire configuration-defined
value is returned.
If this size is greater than the argument
.Fa len ,
the string in
.Fa buf
was truncated.
.Sh ERRORS
The
.Nm confstr
function may fail and set
.Va error
for any of the errors specified for the library functions
.Xr malloc 3
and
.Xr sysctl 3 .
.Pp
In addition, the following errors may be reported:
.Bl -tag -width Er
.It Bq Er EINVAL
The value of the
.Fa name
argument is invalid.
.Sh SEE ALSO
.Xr sysctl 3
.Sh HISTORY
The
.Nm confstr
function first appeared in 4.4BSD.