I have a FILE *, returned by a call to fopen(). I need to get a file descriptor from it, to make calls like fsync(fd) on it. What’s the function to get a file descriptor from a file pointer? 3 Answers 3
I wrote a program for an assignment which is supposed to print its output to stdout. The assignment spec requires the creation of a Makefile which when invoked as make run > outputFile should run the program and write the output to a file, which has a SHA1 fingerprint identical to the one given in … Read more
What is the difference between read() and recv(), and between send() and write() in socket programming in terms of performances, speed and other behaviors? 9 Answers 9
POSIX environments provide at least two ways of accessing files. There’s the standard system calls open(), read(), write(), and friends, but there’s also the option of using mmap() to map the file into virtual memory. When is it preferable to use one over the other? What’re their individual advantages that merit including two interfaces? 6 … Read more
I found this piece of code in /etc/cron.daily/apf #!/bin/bash /etc/apf/apf -f >> /dev/null 2>&1 /etc/apf/apf -s >> /dev/null 2>&1 It’s flushing and reloading the firewall. I don’t understand the >> /dev/null 2>&1 part. What is the purpose of having this in the cron? It’s overriding my firewall rules. Can I safely remove this cron job? … Read more
I am looking for a way to get the output of a command when it is run from within a C++ program. I have looked at using the system() function, but that will just execute a command. Here’s an example of what I’m looking for: std::string result = system(“./some_command”); I need to run an arbitrary … Read more
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. Want to improve this question? Update the question so it’s on-topic for Stack Overflow. Closed 2 years ago. Improve this question I want to kill all processes that I get by: ps aux | grep my_pattern How to do it? … Read more
What is POSIX? I have read the Wikipedia article and I read it every time I encounter the term. The fact is that I never really understood what it is. Can anyone please explain it to me by explaining “the need for POSIX” too? 15 s 15 The most important things POSIX 7 defines C … Read more
In a shell script, how do I echo all shell commands called and expand any variable names? For example, given the following line: ls $DIRNAME I would like the script to run the command and display the following ls /full/path/to/some/dir The purpose is to save a log of all shell commands called and their arguments. … Read more
What command can be used to check if a directory exists or not, within a Bash shell script? 3 36
