Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
After redirecting standard input and output to some files(for example) using freopen how can I redirect them back to where they were at the very beginning?
You can duplicate/clone the initial FD’s using
id = fcntl(blah,F_DUPFD,0), and then usedup2(0,id)to copy it back (after closing stdin!), then reopen the file using fdopen(). Repeat for the others. However, that probably doesn’t get you what you want exactly – it gets you a random filehandle that is associated with FD 0, not changing ‘stdin’.Another kind-of ugly option is to spawn off a thread (which implicitly dups stdin/etc), fdreopen them, do your processing, then exit the thread (closing the reopened stdin/etc) and unblock the main process (which never was changed). This is indirect but probably both portable and guaranteed to work.