Differences

This shows you the differences between two versions of the page.

--- quick_command_list [2014/02/07 18:20] – [For loop replace text with loop value] k2patel
+++ quick_command_list [2022/05/16 20:05] (current) – [remove comments and blank lines from output] k2patel
@@ Line 333: / Line 333: @@
 grep -v -e '^#\|^\W*$'
 </code>
+OR
+<code bash>
+grep '^[[:blank:]]*[^[:blank:]#;]' $file
+</code>
 ==== Calculating Date ====
@@ Line 381: / Line 384: @@
 authconfig --passalgo=sha512 --update
 </code>
+==== sed to search and replace search text and number following ====
+<code bash>
+sed -ie '/serial/s/[0-9][0-9]*/2014050900/'
+</code>
+==== Open postscript file to view ====
+<code bash>
+cat file.ps | ghostview -landscape -
+</code>
+==== Print yum environment ====
+<code bash>
+python -c 'import yum, pprint; yb = yum.YumBase(); pprint.pprint(yb.conf.yumvar, width=1)'
+</code>
+==== Perl Local::lib ====
+Simple easy way to install perl module locally.
+Simply install local::lib
+In order to install module locally use command as shown below.
+<code bash>
+perl -MCPAN -Mlocal::lib -e 'CPAN::install(threads)'
+</code>
+==== Clearing cache linux ====
+Make sure you run **//sync//** command before each command here.\\
+Alternatively you can use
+<code bash>
+sysctl -w vm.drop_caches=<number>
+</code>
+**Free Dentries, Inodes and pagecache from cache memory**
+<code bash>
+echo 3 > /proc/sys/vm/drop_caches
+</code>
+**Free Inodes and Dentries from cache memory**
+<code bash>
+echo 2 > /proc/sys/vm/drop_caches
+</code>
+*Free PageCache from memory**
+<code bash>
+echo 1 > /proc/sys/vm/drop_caches
+</code>
+Writing to /proc/sys/vm/drop_caches allows one to request the kernel immediately drop as much clean cached data as possible.\\
+This will usually result in some memory becoming more obviously available; however, under normal circumstances this should not be necessary.\\
+BE WARNED that using vm.drop_caches can cause a deadlock if the system is under heavy memory and I/O load!!!
+==== Ping packet size ====
+<code bash>
+ping -v -M do -s 8064 192.168.1.1
+</code>
+==== Remove file with ASCII Name ====
+Simplest thing to do is use built in functionality to search and remove in command.
+Here is the file i've on my machine.
+<code bash>
+�^?
+</code>
+which translate to //''$'\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.