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What is a regular expression for a MAC Address?
...x matches pretty much every mac format including Cisco format such as 0102-0304-abcd
^([[:xdigit:]]{2}[:.-]?){5}[[:xdigit:]]{2}$
Example strings which it matches:
01:02:03:04:ab:cd
01-02-03-04-ab-cd
01.02.03.04.ab.cd
0102-0304-abcd
01020304abcd
Mixed format will be matched also!
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UPDATE multiple tables in MySQL using LEFT JOIN
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theprivilegestheprivileges
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How do you use the ellipsis slicing syntax in Python?
...n.
– SwiftsNamesake
Feb 26 '15 at 8:03
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Using async/await for multiple tasks
... 0.02 seconds after test start.
Worker 4 started on thread 13, beginning 0.03 seconds after test start.
Worker 5 started on thread 14, beginning 0.03 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.02 seconds after the test start.
Worker 2 stopped; the wor...
How to create a video from images with FFmpeg?
...video filter instead of -r for the output framerate
ffmpeg -r 1/5 -i img%03d.png -c:v libx264 -vf fps=25 -pix_fmt yuv420p out.mp4
Alternatively the format video filter can be added to the filter chain to replace -pix_fmt yuv420p like "fps=25,format=yuv420p". The advantage of this method is th...
How to convert a std::string to const char* or char*?
...r of NULs - they are given no special treatment by std::string (same in C++03).
In C++03, things were considerably more complicated (key differences highlighted):
x.data()
returns const char* to the string's internal buffer which wasn't required by the Standard to conclude with a NUL (i.e. migh...
How can I extract a good quality JPEG image from a video file with ffmpeg?
...2).
To output a series of images:
ffmpeg -i input.mp4 -qscale:v 2 output_%03d.jpg
See the image muxer documentation for more options involving image outputs.
To output a single image at ~60 seconds duration:
ffmpeg -ss 60 -i input.mp4 -qscale:v 4 -frames:v 1 output.jpg
This will work with any vid...
PostgreSQL - max number of parameters in “IN” clause?
...n on test (cost=0.00..1.30 rows=30 width=208)
-> Hash (cost=0.03..0.03 rows=2 width=4)
-> Values Scan on "*VALUES*" (cost=0.00..0.03 rows=2 width=4)
We can see that postgres build temp table and join with it
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Why should text files end with a newline?
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Source: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_206
An incomplete line as:
A sequence of one or more non- <newline> characters at the end of the file.
Source: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_195
A...
How to add leading zeros for for-loop in shell? [duplicate]
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Use the following syntax:
$ for i in {01..05}; do echo "$i"; done
01
02
03
04
05
Disclaimer: Leading zeros only work in >=bash-4.
If you want to use printf, nothing prevents you from putting its result in a variable for further use:
$ foo=$(printf "%02d" 5)
$ echo "${foo}"
05
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