does perror() set errno?

[ebd]

here the program gives a odd result:

#include <stdio.h>
int main(){
    perror("first");
    perror("next");
    return 0;
}

result:

first: Success
next: Illegal seek

why? any resonable explanation? i found no information about this in man pages.
thanks in advance

[joeBuffer]

According to "C in a Nutshell":

perror
Print an error message corresponding to the value of errno

The perror() function prints a message to the standard error stream. The output includes first the string referenced by the pointer argument, if any; then a colon and a space, then the error message that corresponds to the current value of the errno variable, ending with a newline character.

[ebd]

i know this about perror
i wonder why the sencond perror prints an error, where the error be created?

[gerard4143]

When I copied and ran your program it produced:

first:Success
next:Success

Which is what its supposed to produce. Perror just reports the value of errno...Gerard4143

[joeBuffer]

Works for me, too ...

joebuffer@ubuntu:~/clang$ ./test 
first: Success
next: Success

[drl]

Hi.

According to:

When a system call fails, it usually returns -1 and sets the variable errno to a value describing what went wrong. (These values can be found in <errno.h>.) Many library functions do likewise. The function perror() serves to translate this error code into human-readable form. Note that errno is undefined after a successful library call: this call may well change this variable, even though it succeeds, for example because it internally used some other library function that failed.

-- excerpt from perror(3): print system error message - Linux man page

we might expect both reported results ... cheers, drl