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quick_command_list [2016/05/29 01:20]
k2patel [Print yum environment]
quick_command_list [2022/05/16 20:05] (current)
k2patel [remove comments and blank lines from output]
Line 333: Line 333:
 grep -v -e '​^#​\|^\W*$'​ grep -v -e '​^#​\|^\W*$'​
 </​code>​ </​code>​
 +OR 
 +<code bash> 
 +grep '​^[[:​blank:​]]*[^[:​blank:​]#;​]'​ $file 
 +</​code>​
  
 ==== Calculating Date ==== ==== Calculating Date ====
Line 406: Line 409:
 perl -MCPAN -Mlocal::​lib -e '​CPAN::​install(threads)'​ perl -MCPAN -Mlocal::​lib -e '​CPAN::​install(threads)'​
 </​code>​ </​code>​
 +
 +==== Clearing cache linux ====
 +Make sure you run **//​sync//​** command before each command here.\\
 +Alternatively you can use
 +<code bash>
 +sysctl -w vm.drop_caches=<​number>​
 +</​code>​
 +
 +**Free Dentries, Inodes and pagecache from cache memory**
 +<code bash>
 +echo 3 > /​proc/​sys/​vm/​drop_caches
 +</​code>​
 +
 +**Free Inodes and Dentries from cache memory**
 +<code bash>
 +echo 2 > /​proc/​sys/​vm/​drop_caches
 +</​code>​
 +*Free PageCache from memory**
 +<code bash>
 +echo 1 > /​proc/​sys/​vm/​drop_caches
 +</​code>​
 +
 +Writing to /​proc/​sys/​vm/​drop_caches allows one to request the kernel immediately drop as much clean cached data as possible.\\
 +This will usually result in some memory becoming more obviously available; however, under normal circumstances this should not be necessary.\\
 +BE WARNED that using vm.drop_caches can cause a deadlock if the system is under heavy memory and I/O load!!!
 +
 +==== Ping packet size ====
 +<code bash>
 +ping -v -M do -s 8064 192.168.1.1
 +</​code>​
 +
 +==== Remove file with ASCII Name ====
 +
 +Simplest thing to do is use built in functionality to search and remove in command.
 +Here is the file i've on my machine.
 +<code bash>
 +�^?
 +</​code>​
 +
 +which translate to //''​$'​\250\177'//​ <br>
 +So check or list all the files with ascii in it.
 +<code bash>
 +ls [^[:​ascii:​]]*
 +</​code>​
 +
 +now to remove
 +<code bash>
 +rm [^[:​ascii:​]]*
 +</​code>​
 +
 +:!: Regex can be modified to list all matching file before removal.
 +
 +==== Testing connection or port without any software ====
 +In linux proper way to test tcp or udp port connection without any software installed should be creating dev node.
 +
 +<code bash>
 +/​dev/<​proto>/<​host>/<​port>​
 +</​code>​
 +
 +out put can be redirected to tty with help of cat.
 +<code bash>
 +cat < /​dev/​tcp/​k2patel.in/​3306
 +</​code>​
 +
 +==== Setting id tag on mp3 ====
 +Setting mp3 tag on multiple file based on filename as song name.\\
 +Same artist.
 +<code bash>
 +while read k2; do id3tag -a'xyz guru' -A'​SuperSpeed'​ -s"​${k2%%.*}"​ -y'​2021'​ "​${k2}"​ ; done < <(ls *.mp3)
 +</​code>​
 +
 +==== FFMpeg Conversion of 4K ====
 +I had issue of no audio while playing file over DLNA.\\
 +I've did the transcoding so it can play audio on my Phillips 4K TV.
 +
 +<code bash>
 +ffmpeg -i <​input_file>​.mp4 ​ \
 +    -map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:5 -map 0:12 \
 + -c:v copy \
 + -c:a:0 truehd -strict -2 \
 + -c:a:1 ac3 \
 + -c:s copy \
 + <​output_file>​.mkv
 +</​code>​
 +OR
 +<code bash>
 +ffmpeg -i old_file.mp4 \
 +    -map 0:0 -map 0:1 -map 0:3 -map 0:5 \
 +    -c:v copy \
 +    -c:a:0 ac3 \
 +    -c:s copy \
 +    new_file.mp4
 +</​code>​
 +OR
 +<code bash>
 +ffmpeg -i old_file.mkv \
 +    -map 0:0 -map 0:1 -map 0:2 \
 +    -c:v copy \
 +    -c:a:0 ac3 \
 +    -c:s copy \
 +    -disposition:​s:​0 forced \
 +    new_file.mkv
 +</​code>​
 +
 +  - First thing list all mapping on your existing file using '​ffmpeg -i <​file>​
 +  - Select all streams using map you would like to copy to your new file.
 +  - each map should be listed using map so i selected only 6 out of 12.
 +  - After that specify wich codecs to use.
 +  - in -c:v i'm copying video as is.
 +  - in -c:a:0 i'm converting audio to truehd
 +  - in -c:a:1 i'm also adding second audio stream which is ac3.
 +  - in -c:s i'm copying subtitles.
quick_command_list.1464484845.txt.gz · Last modified: 2020/08/10 02:29 (external edit)