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--- linux_notes [2022/10/04 00:36] – [tput: unknown terminal "xterm-256color"] raju
+++ linux_notes [2023/09/24 15:33] – [what is my OS?] raju
@@ Line 2: / Line 2: @@
   * [[add numbers on the command line]]
   * [[du on month end dates]]
+  * [[change the default shell]]
+  * [[Which shell am I using | Which shell am I using?]]
+  * [[Difference between SHELL and 0 | What is the difference between \$SHELL and \$0?]]
+==== what is my OS? ====
+<code>
+awk -F= '$1=="ID" {print $2}' /etc/os-release
+</code>
+Sample run:
+<code>
+% cat /etc/os-release
+PRETTY_NAME="Debian GNU/Linux 12 (bookworm)"
+NAME="Debian GNU/Linux"
+VERSION_ID="12"
+VERSION="12 (bookworm)"
+VERSION_CODENAME=bookworm
+ID=debian
+HOME_URL="https://www.debian.org/"
+SUPPORT_URL="https://www.debian.org/support"
+BUG_REPORT_URL="https://bugs.debian.org/"
+</code>
+<code>
+% awk -F= '$1=="ID" {print $2}' /etc/os-release
+debian
+</code>
+Ref:
+  * I first came across it in https://github.com/trimclain/.dotfiles/blob/main/Makefile
+==== last reboot times ====
+<code>
+last reboot --time-format full
+</code>
+Sample run
+<code>
+ % last reboot --time-format full
+reboot   system boot  5.10.0-17-amd64  Tue Dec  6 08:18:33 2022   still running
+reboot   system boot  5.10.0-17-amd64  Tue Dec  6 08:11:34 2022 - Tue Dec  6 08:17:36 2022  (00:06)
+reboot   system boot  5.10.0-17-amd64  Tue Dec  6 07:41:53 2022 - Tue Dec  6 08:11:01 2022  (00:29)
+reboot   system boot  5.10.0-17-amd64  Sat Dec  3 13:18:10 2022 - Tue Dec  6 08:11:01 2022 (2+18:52)
+reboot   system boot  5.10.0-17-amd64  Sat Dec  3 13:04:06 2022 - Tue Dec  6 08:11:01 2022 (2+19:06)
+reboot   system boot  5.10.0-17-amd64  Wed Nov 16 11:18:41 2022 - Tue Dec  6 08:11:01 2022 (19+20:52)
+reboot   system boot  5.10.0-17-amd64  Mon Sep  5 21:26:07 2022 - Wed Nov 16 11:18:01 2022 (71+14:51)
+reboot   system boot  5.10.0-16-amd64  Mon Aug 15 05:27:05 2022 - Mon Sep  5 19:36:09 2022 (21+14:09)
+reboot   system boot  5.10.0-16-amd64  Mon Aug  1 17:56:22 2022 - Mon Aug 15 05:26:20 2022 (13+11:29)
+...
+</code>
+{{tag>["reboot history" "show year" "date format"]}}
+==== ls and mv ====
+Sample command
+<code>
+ls -rt *.txt | tail -n5 | tr '\n' '\0' | xargs -0 -i% mv % x1
+</code>
+Notes:
+  * Works even if there are spaces in the filenames. Compare this with <code>
+mv `ls -rt *.txt | tail -n5` x1
+</code> which will not work if there are spaces in the filenames.
+  * Does not work if the filenames contain newline characters.
+Ref:- https://stackoverflow.com/a/937965/6305733
+Related commands
+<code>
+ls -rt *.txt | tail -n5 | tr '\n' '\0' | xargs -0 -i% md5sum %
+</code>
 ==== remove large directories ====
@@ Line 46: / Line 115: @@
 Ref:- https://stackoverflow.com/questions/32798940/tput-unknown-terminal-xterm-256color