Cheat sheet compilation

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################ bash ################
# Get space usage
du -chs ./* | sort -rh
du -kh --max-depth=1 | sort -rh

# find files
find [path] -name "lost+found" -prune -o -name "abc*.log.gz" -print0


################ cpp ################
## cpp heap memory checking
sudo cat /proc/18594/maps |grep heap # cat the process memory

55da5171a000-55da5178a000 rw-p 00000000 00:00 0 [heap]
55da5178a000-55db1c7c3000 rw-p 00000000 00:00 0 [heap]

55db1c7c3000-55da5178a000= 3,406,008,320 around 3G mem.

## Then dump the heap memory to a file(example from UAT):
dd if=/proc/29619/mem bs=1 skip=$((0x55db1c7c3000)) count=$((0x55db1c7c3000-0x55da5178a000)) status=none | strings > /tmp/heap_log.txt

## core dump in linux
$ cat ulimit -c unlimited >> !/.bashrc
$ cat kernel.core_pattern = core.%e.%p.%t >> /etc/sysctl.conf
$ sudo sysctl --system

## check the compiler version with a given binary
$ strings -a <binary/library> | grep "GCC: ("


################ docker compose ################
# up and run in background
docker-compose up -d

# stop --- will keep the data
docker-compose stop

# shutdown --- will remove the data
docker-compose down -v

# check service environment variables
docker-compose run web env

# check config --- this can print the real value of the variable
docker-compose config

################ ssh ################
# check key on agent
$ ssh-add -L
$ ssh-add -l

# add ssh key to agent
$ ssh-add /path/to/your/key

################ conda ################
# create python env from file
$ conda env create --file <env file> --channel default --channel conda-forge
$ conda create --name <env name> python=3.8
# remove python env
$ conda remove -n <env name> --all
# update python env from file
(your_env)$ conda env update --file <env file> --prune

# output environment details
(your_env)$ conda env export | grep -v "^prefix: " > environment.yml

################ pip ################
# pip upgrade package
$ pip install <package> --upgrade
# pip install from file
$ pip install -r requirements.txt
# pip output requirements file
$ pip freeze > requirements.txt
$ pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org -r requirements.txt

################ ffmpeg ################
# extract subtitle from mkv
# https://superuser.com/a/1649387/327808
# 0:s:0 --- input channel:subtitle channel:select channel
$ ffmpeg -i your.mkv -map 0:s:0 your.srt

# concat multiple mp4
# https://stackoverflow.com/questions/7333232/how-to-concatenate-two-mp4-files-using-ffmpeg
$ cat mylist.txt
$ file '/path/to/file.a'
$ file '/path/to/file.b'
$ ffmpeg -f concat -safe 0 -i mylist.txt -c copy c.mp4

# get images from video
# https://stackoverflow.com/questions/40088222/ffmpeg-convert-video-to-images
$ ffmpeg -i test.mp4 -vf fps=1/60 thumb%04d.png # get images for every minute
# https://stackoverflow.com/a/40090033/2358836
$ ffmpeg -i in.mp4 -vf select='between(t,2,6)+between(t,15,24)' -vsync 0 out%d.png # get images in a range

Ubuntu 24.04 tools

Reference

[1]: Subramanian, V. (2024, June 11). NAS RAID Levels Explained: Which Level Is Right For You. Backblaze Blog | Cloud Storage & Cloud Backup. https://www.backblaze.com/blog/nas-raid-levels-explained-choosing-the-right-level-to-protect-your-nas-data/

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