I’m trying to use “select()” to test if a key has been struck and then read it. It sort of works but only if {Enter} is pressed after the character. Sample code is as follows: If I press A nothing happens, but if I Press A{Enter}, the output is: The output is the same if I press ABC{Enter} W…
Tag: select
Meaning of adding 1 on socket file descriptor in select function when using linux socket
What is the meaning of adding 1 on socket file descriptor when using in select function? I create socket file descriptor like below, and use it in select function like below, What is the meaning of +1 in select function? It even does not work when I remove the calculation adding the value. Thanks in advance. …
chaining multiple epoll instances
Can we add file descriptor returned by epoll_create to another epoll instance using epoll_ctl. how do we chain multiple epoll instances in the application, lets say if we have 2 epoll instances one coming from the application and the other coming from library. Please advise. Answer From man epoll Q3 Is the ep…
Linux named fifo non-blocking read select returns bogus read_fds
Similar to the problem asked a while ago on kernel 3.x, but I’m seeing it on 4.9.37. The named fifo is created with mkfifo -m 0666. On the read side it is opened with The resulting fd is passed into a call to select(). Everything works ok, till I run echo >> <fifo-name>. Now the fd appears i…
Select() to read in sockets
I have a client server client connection where the server reads the message sent by the client every 1 second but I do not want the server to keep on waiting for a message for too long. I tried using the select() function but the server continues waiting for some message to read. Could anyone tell me what I a…
Ptrace prevents signal from interrupting pselect() in traced process
I’m trying to monitor syscalls for a binary using ptrace. The binary sleeps in pselect() and without ptrace, a SIGQUIT makes it return from pselect. The mask of blocked signals passed to pselect includes SIGQUIT. When executed with ptrace, it exits from sys_pselect6 but not all the way out of glibc̵…
Select in loop – work all the time – linux
I got next question about select: How to make select in loop ? I try to do like that: But there all the time show: ,, no communicate”. Is it the correct way to create select which work all the time? I am not sure so I prefer to ask. I try to find information in books but with no
select() fails when adding m32 flag to Makefile
i have the following code, which simply creates udp socket to listen to a multicast group. I’m compiling it using gcc, with -c -g flags, on x64 machine. When adding -m32 flag to linking & compiling phases in Makefile, select() call is failing with Invalid Argument. After debugging a little bit with …
Implementing poll in a Linux kernel module
I have a simple character device driver that allows you to read from a custom hardware device. It uses a DMA to copy data from the device’s memory into kernel space (and then up to the user). The read call is very simple. It starts a DMA write, and then waits on a wait queue. When the DMA completes, the