CODEWITHSUNDEEP
macosstdineof
Tzunghsing David Wong
Tzunghsing David Wong

Reputation: 1414

How to continue reading from stdin after Control-D on OS/X

I would like to use EOF to terminate reading bulk user input, but continue to be able to accept user CLI input.

It seems that Linux allows this behaviour, but OS/X simply shuts down the stdin input steam (as seem from the following test program).

Is there any workaround to allow this to work on OS/X?

Sample output from running on MAC OS/X. Once the EOF is detected, no input can be taken. (Lines begin with >>> are output from the program).

TDWONG-M-V08D:$ ./eof_stdin
>>> fgets: zzz
>>> ans=zzz

>>> read stdin again, fgets:
zzz
>>> ans=zzz

TDWONG-M-V08D:$ ./eof_stdin
>>> fgets: >>> ans=
>>> feof(stdin) is true -- EOF detected
>>> read stdin again, fgets:
>>> ans=

Sample output from running on Linux. Input is accepted even after the EOF is detected. (Lines begin with >>> are output from the program).

[tdwong@tdwong-ubuntu tmp]$ ./eof_stdin
>>> fgets: zzz
>>> ans=zzz

>>> read stdin again, fgets:
zzz
>>> ans=zzz

[tdwong@tdwong-ubuntu tmp]$ ./eof_stdin
>>> fgets: >>> ans=
>>> feof(stdin) is true -- EOF detected
>>> read stdin again, fgets:
zzz
>>> ans=zzz

Here is the sample test program:

#include<stdio.h>
int main(void)
{
    char ans[80];
    //
    // read from stdin
    printf(">>> fgets: "); fflush(stdin);
    fgets(ans, sizeof(ans), stdin);
        printf(">>> ans=%s\n", ans);
    if (feof(stdin)) {
        printf(">>> feof(stdin) is true -- EOF detected\n");
    }
    //
    // continue read from stdin
    printf(">>> read stdin again, fgets: \n");
    fgets(ans, sizeof(ans), stdin);
        printf(">>> ans=%s\n", ans);
    return 0;
}

Upvotes: 0

Views: 471

Answers (1)

CRD
CRD

Reputation: 53000

After detecting EOF you can call the stdio function clearerr(stdin), or clearerr_unlocked(stdin), to clear the EOF status on the stdin stream - the man 3 clearerr for more details.

HTH

Upvotes: 1

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