Recently presented 'Data Visualization with PyGal' to the Python Mn Meetup group https://www.meetup.com/PyMNtos-Twin-Cities-Python-User-Group/
A pretty remarkable group, full of very knowledgeable and supportive individuals. I'd highly recommend attending this meetup if you're interested in Python, ranging from beginner to advanced.
I slapped together a video on YouTube for your amusement;
Slides and code segments are available at our GitHub repo: https://github.com/fsk-software/pub
Enjoy.
Seem like every couple months I need to re-look up how to perform numeric formatting with bash. Here's a quick example of how to do it.
$ cat /tmp/go
#!/bin/bash
for i in `seq 100`; do
N=$(printf %03d $i)
echo $N
done
$ ./go
001
002
003
...097
098
099
100
I find doing this that one is no longer the loneliest number, it's paired with a couple of real zeros, but never lonely.
Cheers.
On a number of occasions I found it necessary to locate a list of files by extension (e.g. header/source files) and found that if I needed to locate files of multiple extensions I took the 'cowards way out', executing two 'find' commands and appending the results to a temporary output file, then using the output file as input to the next command in the pipeline (e.g. grep).
e.g.
$ find . -type f -name "*.c*" > /tmp/junk
$ find . -type f -name "*.h*" >> /tmp/junk
$ grep -l SetEvent `cat /tmp/junk`
Every single time I do this, one of the voices in my head will mock me in the manner of Monty Python, apparently one of the voices in my head is from medieval France with a talent for hurling insults.
So, today we begin a short journey to the correct way to utilize the 'or' functionality in a Unix find command.
$ find . -type f \( -name "*.c*" -o -name "*.h*" \) -exec grep -l SetEvent {} \;
The above command will locate all header and implementation files (e.g. *.h, *.hpp, *.c, *.cpp...) and return a list of files that contain the SetEvent expression within them. Note the parenthesis are significant to ensure the or'd list is piped to the exec command, otherwise only the second extension list with run through the exec command.
Cheers.
As we enter our 6th month of self-quarantining, I find the hermit lifestyle no longer to my liking. A virtual friend is needed and this post, my friend, is your ticket to electronic companionship. Enjoy.
# apt-get install espeak
Then, simply run it.
$ espeak "hello, how are you doing?"
Whelp, look at you! You made it to the end you big big overachiever. If you found enjoyment in this particular post, please consider seeking counsel, there are medications and therapy practices that can snap you right quick outta that.
Cheers.
As much as I like using Wireshark, I'm a sucker for a command interface. The trouble is properly defining a filter has been difficult to say the least, boring simple post, but below is a list of brief examples and descriptions.
#!/bin/bash
#--grab the first 10 packets and write to file
tcpdump -c 10 -i wlan0 -w /tmp/data.pcap
#--grab the first 10 packets to/from host and write to file
tcpdump -c 10 -i wlan0 host 192.168.1.125 -w /tmp/data.pcap
#--grab the first 10 packets from host and write to file
tcpdump -c 10 -i wlan0 src host 192.168.1.125 -w /tmp/data.pcap
#--grab the first 10 packets to host and write to file
tcpdump -c 10 -i wlan0 dst host 192.168.1.125 -w /tmp/data.pcap
#--grab the first 10 packets to/from port and write to file
tcpdump -c 10 -i wlan0 port 80 -w /tmp/data.pcap
#--grab the first 10 packets to/from net and write to file
tcpdump -c 10 -i wlan0 net 192.168.1 -w /tmp/data.pcap
#--grab the first 10 packets from network and write to file
tcpdump -c 10 -i wlan0 src net 192.168.1 -w /tmp/data.pcap
#--grab the first 10 packets from network and write to file
tcpdump -c 10 -i wlan0 dst net 192.168.1 -w /tmp/data.pcap
#--grab the first 10 packets from network and write to file
tcpdump -c 10 -i wlan0 '(dst host 192.168.1.125) and (port 443)' -w /tmp/data.pcap
Now, go put your virtual ear to a NIC and hear whatcha hear.
Cheers.
auto int x;
static int y;
Mplayer adopts the 'can do' attitude as a media player. Generally, this utility will play most anything, employs most standard codecs and many that you'll likely never need. If you have a video file, likely you can play it with Mplayer...including raw data.
A past program I was working on grabbed raw LVDS data streams from a Flir infrared camera. First task, confirm the video output is reasonable. Cue investigation of how to play raw data streams without requiring encoding. Mplayer met this need quite nicely. For fun, I thought I'd post some of our findings, hopefully you can find them useful.
Lets start with generating our own raw video stream:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <fcntl.h>
#include <assert.h>
int main()
{
static const int NumFrames = 10;
static const int Width = 640;
static const int Height = 480;
printf("(%s:%d) main process initializing\n",__FILE__,__LINE__);
std::string fileName="/tmp/video.raw";
printf("(%s:%d) fileName='%s'\n",__FILE__,__LINE__,fileName.c_str());
int fp=open(fileName.c_str(),O_CREAT|O_WRONLY|O_TRUNC);
for (int i=0; i<NumFrames; ++i)
{
unsigned char frame[Width*Height];
// generate frame; white box, framed with black lines
memset (frame,255,Width*Height);
for(int c=0; c<Width; ++c) frame[c+Width*0]=0;
for(int c=0; c<Width; ++c) frame[c+Width*(Height-1)]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h+(Width-1)]=0;
// write frame contents to file
for(int k=0; k<Width*Height; ++k)
{
void* tmp=(void*)(frame+k);
int ret=write(fp,tmp,sizeof(unsigned char));
assert(ret==sizeof(unsigned char));
}
}
close(fp);
printf("(%s:%d) main process terminating\n",__FILE__,__LINE__);
return EXIT_SUCCESS;
}
The above code simply generates a sequence of 10 640x480 8-bit grayscale frames, the content of each frame a white background framed with a black one-pixel wide border.
You can play the video contents of this file by issuing the following Mplayer command:
$ mplayer -demuxer rawvideo -rawvideo w=640:h=480:y8:size=307200:fps=1 /tmp/video.raw
A few things worth mentioning; first, since this is a raw video the frame size must be specified (ie. w=640:h=480), the frame rate (fps=1) must be specified as well or it will default to 24fps, giving us little time to review the contents of the video. Lastly, the size=307200 (640*480) is optional at for this format, but will become relevant in later examples. By default, the size will be defined by the width*height, so for this example you could simply not specify the value and all would still be well.
That was fun, but let's give it a little more snap. Suppose you wanted to add some frame metadata following each frame. We'll modify our above example a bit, each frame will be followed by a fixed 28-byte character string identifying the frame number.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <fcntl.h>
#include <assert.h>
int main()
{
static const int NumFrames = 10;
static const int Width = 640;
static const int Height = 480;
printf("(%s:%d) main process initializing\n",__FILE__,__LINE__);
std::string fileName="/tmp/video.raw";
printf("(%s:%d) fileName='%s'\n",__FILE__,__LINE__,fileName.c_str());
int fp=open(fileName.c_str(),O_CREAT|O_WRONLY|O_TRUNC);
for (int i=0; i<NumFrames; ++i)
{
unsigned char frame[Width*Height];
// generate frame; white box, framed with black lines
memset (frame,255,Width*Height);
for(int c=0; c<Width; ++c) frame[c+Width*0]=0;
for(int c=0; c<Width; ++c) frame[c+Width*(Height-1)]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h+(Width-1)]=0;
// write frame contents to file
for(int k=0; k<Width*Height; ++k)
{
void* tmp=(void*)(frame+k);
int ret=write(fp,tmp,sizeof(unsigned char));
assert(ret==sizeof(unsigned char));
}
//write some metadata
char metaData[28];
sprintf(metaData,"frame%04d",i);
assert(write(fp,metaData,sizeof(metaData))==sizeof(metaData));
}
close(fp);
printf("(%s:%d) main process terminating\n",__FILE__,__LINE__);
return EXIT_SUCCESS;
}
Now the frame size becomes a required argument, since the frame size must now account for the metadata, otherwise the metadata would be interpreted as video and you'd have a mess. You can play the above generated video by issuing the command as follows:
$ mplayer -demuxer rawvideo -rawvideo w=640:h=480:y8:size=307228:fps=1 /tmp/video.raw
Ok, now we've learned how to play video with metadata. Our last trick will be playing video with a initial video header.
Let's start by adding some video metadata at the beginning of the video, a 200-byte string.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <fcntl.h>
#include <assert.h>
int main()
{
static const int NumFrames = 10;
static const int Width = 640;
static const int Height = 480;
printf("(%s:%d) main process initializing\n",__FILE__,__LINE__);
std::string fileName="/tmp/video.raw";
printf("(%s:%d) fileName='%s'\n",__FILE__,__LINE__,fileName.c_str());
int fp=open(fileName.c_str(),O_CREAT|O_WRONLY|O_TRUNC);
char videoMetaData[200];
sprintf(videoMetaData,"some cool video");
assert(write(fp,videoMetaData,sizeof(videoMetaData))==sizeof(videoMetaData));
for (int i=0; i<NumFrames; ++i)
{
unsigned char frame[Width*Height];
// generate frame; white box, framed with black lines
memset (frame,255,Width*Height);
for(int c=0; c<Width; ++c) frame[c+Width*0]=0;
for(int c=0; c<Width; ++c) frame[c+Width*(Height-1)]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h]=0;
for(int h=0; h<Height; ++h) frame[0+Width*h+(Width-1)]=0;
// write frame contents to file
for(int k=0; k<Width*Height; ++k)
{
void* tmp=(void*)(frame+k);
int ret=write(fp,tmp,sizeof(unsigned char));
assert(ret==sizeof(unsigned char));
}
//write some metadata
char metaData[28];
sprintf(metaData,"frame%04d",i);
assert(write(fp,metaData,sizeof(metaData))==sizeof(metaData));
}
close(fp);
printf("(%s:%d) main process terminating\n",__FILE__,__LINE__);
return EXIT_SUCCESS;
}
You play this form of video by specifying a start byte offset of 200 and you're set.
$ mplayer -demuxer rawvideo -rawvideo w=640:h=480:y8:size=307228:fps=1 -sb 200 /tmp/video.raw
Loved my old phone but recently replaced it. Result is that I have a relatively decent smart phone with little, to no, purpose in life. Repurposing as a RTSP server device seemed like a reasonable task.
Reviewed a series of video server apps in the Google Play Store, but only one that worked well for me with Linux RTSP clients was:
https://play.google.com/store/apps/details?id=com.pas.webcam
After installing the app and short configuration, you start the server by clicking the 'Start server' button in the video preference activity.
Once the phone streaming is running, it displays a live view of the scene and the connection URL.
Open it with VLC and you're cookin' with bacon:
$ cvlc http://192.168.0.157:8080/video
Voilà .
#!/usr/bin/tclsh
proc log { msg } {# puts stderr __$msg}
proc mean { L } { set sum 0.0 foreach e $L { set sum [expr $sum + $e] } return [expr $sum / [llength $L].]}
proc median { L } { set L1 [lsort -real $L] return [lindex $L1 [expr [llength $L1] / 2]]}
proc process { fileName } { set fp [open $fileName r] while { [gets $fp line] >= 0 } { switch -glob -- $line { *Cpu* { log "processing line '$line'" set el [split $line ,] set userLoad [string trimleft [lindex $el 0] "Cpu(s):"] set sysLoad [lindex $el 1] set niceLoad [lindex $el 2] set idleLoad [lindex $el 3] log "parsing $userLoad" log "parsing $sysLoad" log "parsing $niceLoad" log "parsing $idleLoad" set userLoad [lindex [split $userLoad \%] 0] set sysLoad [lindex [split $sysLoad \%] 0] set niceLoad [lindex [split $niceLoad \%] 0] set idleLoad [lindex [split $idleLoad \%] 0] log "extracted $userLoad" log "extracted $sysLoad" log "extracted $niceLoad" log "extracted $idleLoad"# puts [expr $userLoad+$sysLoad+$niceLoad+$idleLoad] lappend L [expr 100.0-$idleLoad] } } } close $fp puts "mean cpu load: [mean $L]" puts "median cpu load: [median $L]"}
proc monitorCpuLoad { fileName duration } { catch { exec top -b -n $duration -d 1 > $fileName } process $fileName}
proc help { } { upvar #0 argv0 argv0 puts stderr "usage: $argv0 \[logFileName\] \[duration\]" exit}
#---main--- if { [llength $argv] != 2 } { help } monitorCpuLoad [lindex $argv 0] [lindex $argv 1]
