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diff --git a/man-pages-posix-2017/man3p/putenv.3p b/man-pages-posix-2017/man3p/putenv.3p new file mode 100644 index 0000000..4fcbfd1 --- /dev/null +++ b/man-pages-posix-2017/man3p/putenv.3p @@ -0,0 +1,161 @@ +'\" et +.TH PUTENV "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +This manual page is part of the POSIX Programmer's Manual. +The Linux implementation of this interface may differ (consult +the corresponding Linux manual page for details of Linux behavior), +or the interface may not be implemented on Linux. +.\" +.SH NAME +putenv +\(em change or add a value to an environment +.SH SYNOPSIS +.LP +.nf +#include <stdlib.h> +.P +int putenv(char *\fIstring\fP); +.fi +.SH DESCRIPTION +The +\fIputenv\fR() +function shall use the +.IR string +argument to set environment variable values. The +.IR string +argument should point to a string of the form "\c +.IR name =\c +.IR value \c +\&". +The +\fIputenv\fR() +function shall make the value of the environment variable +.IR name +equal to +.IR value +by altering an existing variable or creating a new one. In either +case, the string pointed to by +.IR string +shall become part of the environment, so altering the string shall +change the environment. +.P +The +\fIputenv\fR() +function need not be thread-safe. +.SH "RETURN VALUE" +Upon successful completion, +\fIputenv\fR() +shall return 0; otherwise, it shall return a non-zero value and set +.IR errno +to indicate the error. +.SH ERRORS +The +\fIputenv\fR() +function may fail if: +.TP +.BR ENOMEM +Insufficient memory was available. +.LP +.IR "The following sections are informative." +.SH EXAMPLES +.SS "Changing the Value of an Environment Variable" +.P +The following example changes the value of the +.IR HOME +environment variable to the value +.BR /usr/home . +.sp +.RS 4 +.nf + +#include <stdlib.h> +\&... +static char *var = "HOME=/usr/home"; +int ret; +.P +ret = putenv(var); +.fi +.P +.RE +.SH "APPLICATION USAGE" +The +\fIputenv\fR() +function manipulates the environment pointed to by +.IR environ , +and can be used in conjunction with +\fIgetenv\fR(). +.P +See +\fIexec\fR() +for restrictions on changing the environment in multi-threaded +applications. +.P +This routine may use +\fImalloc\fR() +to enlarge the environment. +.P +A potential error is to call +\fIputenv\fR() +with an automatic variable as the argument, then return from the +calling function while +.IR string +is still part of the environment. +.P +Although the space used by +.IR string +is no longer used once a new string which defines +.IR name +is passed to +\fIputenv\fR(), +if any thread in the application has used +\fIgetenv\fR() +to retrieve a pointer to this variable, it should not be freed by calling +\fIfree\fR(). +If the changed environment variable is one known by the system (such as +the locale environment variables) the application should never free the +buffer used by earlier calls to +\fIputenv\fR() +for the same variable. +.P +The +\fIsetenv\fR() +function is preferred over this function. One reason is that +\fIputenv\fR() +is optional and therefore less portable. Another is that using +\fIputenv\fR() +can slow down environment searches, as explained in the RATIONALE +section for +.IR "\fIgetenv\fR\^(\|)". +.SH RATIONALE +Refer to the RATIONALE section in +.IR "\fIsetenv\fR\^(\|)". +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIexec\fR\^", +.IR "\fIfree\fR\^(\|)", +.IR "\fIgetenv\fR\^(\|)", +.IR "\fImalloc\fR\^(\|)", +.IR "\fIsetenv\fR\^(\|)" +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "\fB<stdlib.h>\fP" +.\" +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1-2017, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 7, 2018 Edition, +Copyright (C) 2018 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. +In the event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . +.PP +Any typographical or formatting errors that appear +in this page are most likely +to have been introduced during the conversion of the source files to +man page format. To report such errors, see +https://www.kernel.org/doc/man-pages/reporting_bugs.html . |