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lib/libc/string/strerror.3

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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.\" @(#)strerror.3 8.1 (Berkeley) 6/9/93 .\" @(#)strerror.3 8.1 (Berkeley) 6/9/93
.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd April 5, 2011 .Dd December 15, 2020
.Dt STRERROR 3 .Dt STRERROR 3
.Os .Os
.Sh NAME .Sh NAME
.Nm perror , .Nm perror ,
.Nm strerror , .Nm strerror ,
.Nm strerror_r , .Nm strerror_r ,
.Nm sys_errlist , .Nm sys_errlist ,
.Nm sys_nerr .Nm sys_nerr
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.Va sys_nerr .Va sys_nerr
contains a count of the messages in contains a count of the messages in
.Va sys_errlist . .Va sys_errlist .
The use of these variables is deprecated; The use of these variables is deprecated;
.Fn strerror .Fn strerror
or or
.Fn strerror_r .Fn strerror_r
should be used instead. should be used instead.
.Sh EXAMPLES
The following example shows how to use
.Fn perror
to report an error.
.Bd -literal -offset 2n
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int
main(void)
yuripvUnsubmitted
Done
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#include <unistd.h>
int
- main()
+ main(void)
{
if (pipe(NULL) < 0) {
yuripv:
{
if (pipe(NULL) < 0) {
jillesUnsubmitted
Not Done
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This is not a great example since it is undefined behaviour. In fact, before FreeBSD 11.0, this caused a segmentation fault instead of an error return.

Perhaps a better example is fd = open("/dev/null/wrong", O_RDONLY); which will fail with Not a directory.

jilles: This is not a great example since it is undefined behaviour. In fact, before FreeBSD 11.0, this…
0mpAuthorUnsubmitted
Done
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Ha, fascinating! Thanks a lot, I'll update the revision shortly.

0mp: Ha, fascinating! Thanks a lot, I'll update the revision shortly.
perror("pipe()");
exit(1);
}
return (0);
}
.Ed
.Pp
When executed, the program will print an error message along the lines of
.Ql pipe(): Bad address .
.Sh SEE ALSO .Sh SEE ALSO
.Xr intro 2 , .Xr intro 2 ,
.Xr err 3 , .Xr err 3 ,
.Xr psignal 3 .Xr psignal 3
.Sh STANDARDS .Sh STANDARDS
The The
.Fn perror .Fn perror
and and
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