Section: POSIX Programmer's Manual (3P)
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.
--- compare part of two strings
int strncmp(const char *s1, const char *s2, size_t n);
The functionality described on this reference page is aligned with the
ISO C standard. Any conflict between the requirements described here and the
ISO C standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C standard.
function shall compare not more than
bytes (bytes that follow a NUL character are not compared) from the array
pointed to by
to the array pointed to by
The sign of a non-zero return value is determined by the sign of the
difference between the values of the first pair of bytes (both
interpreted as type
that differ in the strings being compared.
Upon successful completion,
shall return an integer greater than, equal to, or less than 0, if the
possibly null-terminated array pointed to by
is greater than, equal to, or less than the possibly null-terminated
array pointed to by
No errors are defined.
The following sections are informative.
The Base Definitions volume of POSIX.1-2017,
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
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