I am doing some file IO with c code. I have a particular pattern in my file. I can verify this by a shell command cat abc.txt | grep abc | wc -l. When I execute the same command using System(), it give proper output, but I have no clue how can I get its output into a variable and
Tag: linux
How to change Keyboard Layout (a X11 API solution)
I want to change keyboard layout in Linux by programming, What X11’s API function does this? Answer I found one good solution. It’s a c++ class wrriten by Jay Bromley, that I can add to my app and using it. source code It’s very easy to use: you can read source code and found some another us…
C write() doesn’t send data until close(fd) is called
So I have this test code to send “HELLO” over a USB serial port: The program executes fine and “HELLO” is sent but there is one problem. “HELLO” doesn’t seem to be sent when the write() function is called, but rather when the file descriptor is closed. I added the sle…
Retaining file permissions with Git
I want to version control my web server as described in Version control for my web server, by creating a git repo out of my /var/www directory. My hope was that I would then be able to push web content from our dev server to github, pull it to our production server, and spend the rest of the day at
python xinetd client disconnection handling
This may or may not being a coding issue. It may also be an xinetd deamon issue, i do not know. I have a python script which is triggered from a linux server running xinetd. Xinetd has been setup to only allow one instance as I only want one machine to be able to connect to the service, which is
TCP performance differences between RH Linux and Solaris in java?
While comparing java TCP socket performance between RH Linux and Solaris, one of my test is done by using a java client sending strings and reading the replies from a java echo server. I measure the time spent to send and receive the data (i.e. the loop back round trip). The test is run 100,000 times (more oc…
How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?
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? Answer The proper function is int fileno(FILE *stream). It can be found in <stdio.h>, and is a POSIX standa…
Whats the difference between sed -E and sed -e
I’m working on some old code and I found that I used to use but I now try It seems to do the same thing, or does it? I kinda remember there being a reason I done it but I can’t remember and doing “man sed” doesn’t help as they don’t have anything about -E only -e that doesn…
Linux, timerfd accuracy
I have a system that needs at least 10 mseconds of accuracy for timers. I went for timerfd as it suits me perfectly, but found that even for times up to 15 milliseconds it is not accurate at all, either that or I don’t understand how it works. The times I have measured were up to 21 mseconds on a
How to convert large SVG file to tiled PNGs?
I have a large SVG file (approx. 60 MB, 10000×10000 pixels but with the potential to get much larger), and I’m wanting to create, say, many tiled 256×256 PNG images from it (in that example there would be 1600 images; round(10000/256)^2). Does anyone have any idea of how to do this on a web se…