.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" References consulted:
.\" Linux libc source code
.\" 386BSD man pages
.\" Modified Mon Mar 29 22:41:16 1993, David Metcalfe
.\" Modified Sat Jul 24 21:35:16 1993, Rik Faith (faith@cs.unc.edu)
-.TH BSEARCH 3 2003-11-01 "" "Linux Programmer's Manual"
+.TH BSEARCH 3 2017-09-15 "" "Linux Programmer's Manual"
.SH NAME
bsearch \- binary search of a sorted array
.SH SYNOPSIS
.nf
.B #include <stdlib.h>
-.sp
-.BI "void *bsearch(const void *" key ", const void *" base ", size_t " nmemb ,
-.RS
-.BI "size_t " size ", int (*" compar ")(const void *, const void *));"
-.RE
+.PP
+.BI "void *bsearch(const void *" key ", const void *" base ,
+.BI " size_t " nmemb ", size_t " size ,
+.BI " int (*" compar ")(const void *, const void *));"
.fi
.SH DESCRIPTION
-The \fBbsearch\fP() function searches an array of \fInmemb\fP objects,
-the initial member of which is pointed to by \fIbase\fP, for a member
-that matches the object pointed to by \fIkey\fP. The size of each member
-of the array is specified by \fIsize\fP.
+The
+.BR bsearch ()
+function searches an array of
+.I nmemb
+objects,
+the initial member of which is pointed to by
+.IR base ,
+for a member
+that matches the object pointed to by
+.IR key .
+The size of each member
+of the array is specified by
+.IR size .
.PP
The contents of the array should be in ascending sorted order according
-to the comparison function referenced by \fIcompar\fP. The \fIcompar\fP
-routine is expected to have two arguments which point to the \fIkey\fP
+to the comparison function referenced by
+.IR compar .
+The
+.I compar
+routine is expected to have two arguments which point to the
+.I key
object and to an array member, in that order, and should return an integer
-less than, equal to, or greater than zero if the \fIkey\fP object is found,
+less than, equal to, or greater than zero if the
+.I key
+object is found,
respectively, to be less than, to match, or be greater than the array
member.
-.SH "RETURN VALUE"
-The \fBbsearch\fP() function returns a pointer to a matching member of the
-array, or NULL if no match is found. If there are multiple elements that
+.SH RETURN VALUE
+The
+.BR bsearch ()
+function returns a pointer to a matching member of the
+array, or NULL if no match is found.
+If there are multiple elements that
match the key, the element returned is unspecified.
+.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 bsearch ()
+T} Thread safety MT-Safe
+.TE
+.sp 1
+.SH CONFORMING TO
+POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
.SH EXAMPLE
The example below first sorts an array of structures using
.BR qsort (3),
then retrieves desired elements using
.BR bsearch ().
-.sp
-.nf
+.PP
+.EX
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct mi {
- int nr;
- char *name;
+ int nr;
+ char *name;
} months[] = {
- { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
- { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
- { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
+ { 1, "jan" }, { 2, "feb" }, { 3, "mar" }, { 4, "apr" },
+ { 5, "may" }, { 6, "jun" }, { 7, "jul" }, { 8, "aug" },
+ { 9, "sep" }, {10, "oct" }, {11, "nov" }, {12, "dec" }
};
#define nr_of_months (sizeof(months)/sizeof(months[0]))
-static int compmi(const void *m1, const void *m2) {
- struct mi *mi1 = (struct mi *) m1;
- struct mi *mi2 = (struct mi *) m2;
- return strcmp(mi1\->name, mi2\->name);
+static int
+compmi(const void *m1, const void *m2)
+{
+ struct mi *mi1 = (struct mi *) m1;
+ struct mi *mi2 = (struct mi *) m2;
+ return strcmp(mi1\->name, mi2\->name);
}
-int main(int argc, char **argv) {
- int i;
+int
+main(int argc, char **argv)
+{
+ int i;
- qsort(months, nr_of_months, sizeof(struct mi), compmi);
- for (i = 1; i < argc; i++) {
- struct mi key, *res;
- key.name = argv[i];
- res = bsearch(&key, months, nr_of_months,
- sizeof(struct mi), compmi);
- if (res == NULL)
- printf("'%s': unknown month\en", argv[i]);
- else
- printf("%s: month #%d\en", res->name, res->nr);
- }
- return 0;
+ qsort(months, nr_of_months, sizeof(struct mi), compmi);
+ for (i = 1; i < argc; i++) {
+ struct mi key, *res;
+ key.name = argv[i];
+ res = bsearch(&key, months, nr_of_months,
+ sizeof(struct mi), compmi);
+ if (res == NULL)
+ printf("\(aq%s\(aq: unknown month\en", argv[i]);
+ else
+ printf("%s: month #%d\en", res\->name, res\->nr);
+ }
+ exit(EXIT_SUCCESS);
}
-.fi
+.EE
.\" this example referred to in qsort.3
-.SH "CONFORMING TO"
-SVr4, 4.3BSD, POSIX.1-2001, C89, C99
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR hsearch (3),
.BR lsearch (3),
.BR qsort (3),
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