'\" te .\" Copyright (c) 2002, Sun Microsystems, Inc. All Rights Reserved Portions Copyright (c) 1992, X/Open Company Limited All Rights Reserved .\" Sun Microsystems, Inc. gratefully acknowledges The Open Group for permission to reproduce portions of its copyrighted documentation. Original documentation from The Open Group can be obtained online at http://www.opengroup.org/bookstore/. .\" The Institute of Electrical and Electronics Engineers and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase "this text" refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions 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. This notice shall appear on any product containing this material. .TH index 3C "24 Jul 2002" "SunOS 5.11" "Standard C Library Functions" .SH NAME index, rindex \- string operations .SH SYNOPSIS .LP .nf #include \fBchar *\fR\fBindex\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR); .fi .LP .nf \fBchar *\fR\fBrindex\fR(\fBconst char *\fR\fIs\fR, \fBint\fR \fIc\fR); .fi .SH DESCRIPTION .sp .LP The \fBindex()\fR and \fBrindex()\fR functions operate on null-terminated strings. .sp .LP The \fBindex()\fR function returns a pointer to the first occurrence of character \fIc\fR in string \fIs\fR. .sp .LP The \fBrindex()\fR function returns a pointer to the last occurrence of character \fIc\fR in string \fIs\fR. .sp .LP Both \fBindex()\fR and \fBrindex()\fR return a null pointer if \fIc\fR does not occur in the string. The null character terminating a string is considered to be part of the string. .SH USAGE .sp .LP On most modern computer systems, you can \fInot\fR use a null pointer to indicate a null string. A null pointer is an error and results in an abort of the program. If you wish to indicate a null string, you must use a pointer that points to an explicit null string. On some machines and with some implementations of the C programming language, a null pointer, if dereferenced, would yield a null string. Though often used, this practice is not always portable. Programmers using a null pointer to represent an empty string should be aware of this portability issue. Even on machines where dereferencing a null pointer does not cause an abort of the program, it does not necessarily yield a null string. .SH ATTRIBUTES .sp .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS tab() box; lw(2.75i) |lw(2.75i) lw(2.75i) |lw(2.75i) . \fBATTRIBUTE TYPE\fR\fBATTRIBUTE VALUE\fR _ Interface StabilityStandard .TE .SH SEE ALSO .sp .LP \fBbstring\fR(3C), \fBmalloc\fR(3C), \fBstring\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)