.TH LIBSIMPLE_VPUTENVF 3 2018-10-20 libsimple
.SH NAME
libsimple_vputenvf \- change or add a string formatted value to the environment
.SH SYNOPSIS
.nf
#include <libsimple.h>

int libsimple_vputenvf(const char *\fIfmt\fP, va_list \fIap\fP);
static inline int libsimple_putenvf(const char *\fIfmt\fP, ...);
void libsimple_envputenvf(int \fIstatus\fP, const char *\fIfmt\fP, va_list \fIap\fP);
static inline void libsimple_enputenvf(int \fIstatus\fP, const char *\fIfmt\fP, ...);
static inline void libsimple_evputenvf(const char *\fIfmt\fP, va_list \fIap\fP);
static inline void libsimple_eputenvf(const char *\fIfmt\fP, ...);

#ifndef vputenvf
# define vputenvf libsimple_vputenvf
#endif
#ifndef putenvf
# define putenvf libsimple_putenvf
#endif
#ifndef envputenvf
# define envputenvf libsimple_envputenvf
#endif
#ifndef enputenvf
# define enputenvf libsimple_enputenvf
#endif
#ifndef evputenvf
# define evputenvf libsimple_evputenvf
#endif
#ifndef eputenvf
# define eputenvf libsimple_eputenvf
#endif
.fi
.PP
Link with
.IR \-lsimple .
.SH DESCRIPTION
The
.BR libsimple_vputenvf ()
function constructs a string using the
.BR vsprintf (3)
function, and adds it to the environment, overriding
its old value if it already exists. The string shall be on
the format \fB\(dq\fP\fIname\fP\fB=\fP\fIvalue\fP\fB\(dq\fP;
however this is not strictly enforced, see
.BR NOTES .
The parameter
.I fmt
is used as the format string for the
.BR vsprintf (3)
function, and the parameter
.I ap
is used as the formatting arguments.
.PP
The
.BR libsimple_putenvf ()
function is a version of the
.BR libsimple_vputenvf ()
that uses variadic arguments instead of
.IR va_list .
.PP
The
.BR libsimple_envputenvf ()
and
.BR libsimple_evputenvf ()
functions are versions of the
.BR libsimple_vputenvf ()
function that call the
.BR libsimple_enprintf (3)
function on failure, causing the process to print
an error message and exit. See
.BR libsimple_enprintf ()
for more information.
.PP
The
.BR libsimple_enputenvf ()
and
.BR libsimple_eputenvf ()
functions are versions of the
.BR libsimple_putenvf ()
function that call the
.BR libsimple_enprintf (3)
function on failure, causing the process to print
an error message and exit. See
.BR libsimple_enprintf ()
for more information.
.PP
Modifications made to the environment do not become
visible to other process until the process image is
changed.
.SH RETURN VALUE
Upon  successful  completion, the
.BR libsimple_vputenvf ()
and
.BR libsimple_putenvf ()
functions return 0; otherwise, they return \-1 and set
.I errno
to indicate the error.
.SH ERRORS
The
.BR libsimple_vputenvf ()
and
.BR libsimple_putenvf ()
functions will fail if:
.TP
.B EINVAL
The construct string is empty or starts with the
.B '='
character.
.TP
.B ENOMEM
Insufficient memory was available.
.PP
They may also fail for any reason specified for the
.BR vsnprintf (3)
function.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lb
l l l.
Interface	Attribute	Value
T{
.BR libsimple_vputenvf (),
.br
.BR libsimple_putenvf (),
.br
.BR libsimple_envputenvf (),
.br
.BR libsimple_enputenvf (),
.br
.BR libsimple_evputenvf (),
.br
.BR libsimple_eputenvf ()
T}	Thread safety	MT-Safe env
T{
.BR libsimple_vputenvf (),
.br
.BR libsimple_putenvf (),
.br
.BR libsimple_envputenvf (),
.br
.BR libsimple_enputenvf (),
.br
.BR libsimple_evputenvf (),
.br
.BR libsimple_eputenvf ()
T}	Async-signal safety	AS-Safe
T{
.BR libsimple_vputenvf (),
.br
.BR libsimple_putenvf (),
.br
.BR libsimple_envputenvf (),
.br
.BR libsimple_enputenvf (),
.br
.BR libsimple_evputenvf (),
.br
.BR libsimple_eputenvf ()
T}	Async-cancel safety	AC-Safe
.TE
.SH EXAMPLES
None.
.SH APPLICATION USAGE
None.
.SH RATIONALE
None.
.SH FUTURE DIRECTIONS
None.
.SH NOTES
If the construct does not contain the
.B '='
character, it may still be added to the environment,
however this can cause problem for some programs, and
the behaviour is unspecified when countered by the
.BR getenv (3),
.BR putenv (3),
.BR setenv (3),
and
.BR unsetenv (3)
functions.
.SH BUGS
There is no mechanism for detecting which entries in the
environment are statically allocated and which are
dynamically allocated, this can lead to memory leaks
with are detected by
.BR valgrind (1).
.SH SEE ALSO
.BR putenv (3),
.BR setenv (3),
.BR unsetenv (3),
.BR getenv (3),
.BR environ (3)