freopen reopens a stream with a different file or mode.
Reuses stream to either open the file specified by filename or to change its access mode.
Reference: freopen
Questions tagged [freopen]
105 questions
2
votes
1 answer
freopen not writing to the specified file
I am trying to redirect output of stdout and stderr using a file. I am using freopen and it creates the file in the correct directory but the file is blank. When I comment out the code to redirect the stdout and stderr - the output shows up on the…
user1185853
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2
votes
1 answer
Why does reopening stdout to a newly-allocated console occasionally fail?
Consider this program:
#include
#include
#pragma comment(linker, "/SUBSYSTEM:CONSOLE")
int main(void) {
if (!FreeConsole()) {
MessageBoxA(NULL, "FreeConsole failed", NULL, MB_ICONHAND);
return 1;
}
…
Joseph Sible-Reinstate Monica
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2
votes
1 answer
Having child processes printf to redirected stdout correctly
I am redirecting stdout on a process with freopen(), and as long as it's just one process, everything's fine.
However, if I do something like this:
freopen("stdout.txt", "a+", stdout);
printf("Initial line.\n");
int i=0;
while(i<1000)
{
…
Jim
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- 5
2
votes
0 answers
when stdout is redirected to a file fflush is not enough
I have a C program with 9 calls to printf and I need it to run on a remote server for several days. So I decided to redirect the stdout to a file to check the progresses:
FILE *foutput=freopen("output.txt","w",stdout);
After some debugging I found…
GRquanti
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2
votes
2 answers
How to write in stdout after using freopen
After freopen-ing stdout, How can I print on terminal?
freopen("out", "w", stdout); // reopen stdout
/* something */
printf("Now I want to print this on terminal");
cijianzy
- 71
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- 8
2
votes
1 answer
Fortran equivalent of freopen
In C I can use the standard function freopen with stdout to redirect the standard output of my program to a file. I would like to do the same with fortran, but after having googled I couldn't find a similar feature. Does it exist?
In case somebody…
Spiros
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2
votes
1 answer
Should "freopen'ed" stdout be closed?
In a C or C++ program I can use freopen to redirect the output (i.e. the stdout file descriptor) to another file (or to discard it be reopening the file descriptor to /dev/null or another sink).
The question is: if I do so, should I take care of…
Spiros
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- 42
2
votes
1 answer
freopen or freopen_s, what exactly are they doing?
errno_t freopen_s ( FILE** pFile, const char *path, const char *mode, FILE *stream );
Here, the freopen_s disassociates the FILE pointer stream from whatever it is pointing at, then associates it with the file that is located at path. The mode…
Utkan Gezer
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2
votes
3 answers
freopen again but still can't read after fseek
I have something as below in c++.
I want to read a file for several times, but failed.
Though I use fseek to move to the head of the file after I freopen again, but I still can only read it once. For the second time, cin get nothing @.@.
I'm really…
user2759293
- 23
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2
votes
1 answer
Check the return value of freopen() in C
I'm aware that the right use of freopen is to omit the assignment, given this post:
freopen("/dev/tty","r", stdin);
My question is, should I still check the return value? I'm reopening stdin and closing whatever it was. For…
user1024718
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2
votes
1 answer
freopen_s on stdout causes problems with GetConsoleScreenBufferInfo on Windows
To temporarily redirect stdout to a file, I'm doing:
printf("Before");
freopen_s(&stream, "test.txt", "w", stdout);
printf("During");
freopen_s(&stream, "CONOUT$", "w", stdout);
printf("After");
That works, however doing:
CONSOLE_SCREEN_BUFFER_INFO…
Sydius
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2
votes
2 answers
reassign a file pointer in loop
I need to reassign a single file pointer to multiple files sequentially.
I have the file paths correctly in a string path.
when i pass the path and the file pointer to a function to reassign, I get "Aborted (core dumped)"..
FILE * fptr; …
tabs_over_spaces
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2
votes
1 answer
Does it make sense to try and reopen a tty in binary mode?
I have stumbled on this C code. It uses freopen to reopen stdin in binary mode:
if (!isatty(STDIN_FILENO))
freopen(NULL, "rb", stdin);
I don't understand where the isatty test comes from. Does it mean that it does not make sense to reopen a…
epsicot
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2
votes
1 answer
sending output stream to char[] in c
I have been using dup and freopen to rerout stdout to a file as below:
fflush(stdout);
fgetpos(stdout, &pos);
fd = dup(fileno(stdout));
freopen("stdout.out", "w", stdout);
What I would like to do would be rerout it to a char[], so that I can…
ewok
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2
votes
1 answer
Mixing freopen and ncurses
I'm having issues in mixing freopen of stdin together with ncurses library.
What I do is to reopen the stdin to a file, parse it through flex+bison, then I should revert it back and start ncurses.
Code for the swap is the following:
void…
Jack
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