What is the purpose of a shell command (part of a shell script) starting with an exclamation mark? Concrete example: In foo.sh: I know that without the space the exclamation mark is used for history replacements and ! <expression> according to the man page can be used to evaluate “True if expr is …
Tag: linux
Error installing minqa in a non-standard location in Scientific Linux 6.6
I would ultimately like to install lme4 for R-3.2.5 on a system with Scientific Linux 6.6. I’m on a shared system (I’m compiling R packages for a distributed computing problem), so I need to install all the packages to a non-standard location (/a/lot/of/subdirectories/R-3.2.5 instead of the usual …
What HW resource is mostly used when one does memcpy()?
This feels like a very newbie question, but I suddenly find myself clueless. I’m trying to profile a c application that does a lot of memory copies, and there is an option for me to reduce that number (requires some re-design). I’m trying to realize if it’s worth it, but I have no idea what …
Create directories and download files by reading input from a file
Hi! I have this piece of code that reads field by field from the file specified. What I am trying to do here is I am creating a directory that is specified in second field and then I am downloading file specified in first field and then after having that file downloaded I am that file in the directory specifi…
Linux cat and less output for my text file is different from gedit and other gnome editor
I redirected ri’s ruby Array doc into a file but it didn’t look good in gedit. But text looks just fine in cli. That’s how my file looks in terminal editors. Everything is fine here. But when I open it in gedit or other gnome editors, that’s how it looks like. Some specific words look …
C Linux Pipe Reading Out-of-Order. Missing, and Duplicated Output
I am working on an application that needs to launch arbitrary child processes and read their output while they are running. It might be useful to think of it as a terminal emulator because it has to be able to run child processes many times throughout it’s lifetime and read back their output, and I want…
“mkdir || echo && exit” exiting even when mkdir succeeds
mkdir $2 || echo “I can’t create directory $2” && exit 8 Hi everyone, this is my first post here, so be kind. I am making a script right now and this line troubles me. The exit 8 should happen only if the directory $2 cannot be created. After running the script and successfully creat…
Server not accepting request on port 9999
I am trying to deploy my socket[phpws library] on amazon EC2 instance. For this I deployed code and run socket. I have selected port 9999 for socket handshake, but it is not working. I tried to captured request on this server by command : Then I hit this port, I did not received any request. I thought this is…
Get notified about process termination
I’m trying to use NETLINK with CN_IDX_PROC to monitor my process. This works but requires the monitoring process to be launched with root privileges. I’ve tried to fix it by setting a capability in the filesystem on my monitoring executable (including CAP_AUDIT_READ, CAP_SYS_ADMIN,CAP_SYS_PTRACE and CAP_IPC_O…
c++ thread_local destructors with pthread destructors
I want to do some work after all C++ thread_local destructors called. This is platform specific – Android, so I have access to pthreads. The question is, when pthread_key_created destructors should be called, before or after C++ thread_local destructors? Or they can be interleaved? I tested On Linux Min…