.Dd September 27, 2015
.Dt ERR 3
.Os
.Sh NAME
.Nm err
.Nd format an error message
.Sh SYNOPSIS
.In errno.h
.Vt extern int errno ;
.Fd #define EPERM 1
.Fd #define ENOENT 2
.Fd #define ESRCH 3
.Fd #define EINTR 4
.In err.h
.Ft void
.Fo err
.Fa "int eval"
.Fa "const char *fmt"
.Fa ...
.Fc
.Sh DESCRIPTION
If the variable
.Va errno
has the value
.Er ENOENT ,
the function
.Fn err
prints the message
.Dq \&No such file or directory .
.Pp
Note that some of the macros differ between SYNOPSIS and DESCRIPTION:
.Bl -dash
.It
When citing the type of a global variable, even when followed by the name, use
.Ic \&Vt .
When citing the name only, use
.Ic \&Va .
.It
When citing a complete preprocessor definition line in the SYNOPSIS, use
.Ic \&Fd .
When mentioning the defined constant only, use
.Ic \&Dv ,
or
.Ic \&Er
if it's an error number.
.It
The name of a function with multiple arguments appears behind
.Ic \&Fo
in the SYNOPSIS.
When mentioning the function name again in isolation, use
.Ic \&Fn .
.El
.Pp
The error message itself sets a minor trap:
It needs to be quoted, either by prepending a zero-width space
.Pq Sq \e& ,
or by enclosing it in double quotes.
Otherwise, the word
.Sq \&No
is misinterpreted as the macro
.Ic \&No
and hence lost from the output.