Today I learned
A new initiative to record what I have learned in an attempt to apply it in my life.
Linux Command Line
In studying for the lpic-1 I am learning lot's of little things that I didn't know...
help
Bash has a help function called help.
$ help while
while: while COMMANDS; do COMMANDS; done
Execute commands as long as a test succeeds.
Expand and execute COMMANDS as long as the final command in the
`while' COMMANDS has an exit status of zero.
Exit Status:
Returns the status of the last command executed.
This will be very handy, wish I knew about years ago.
apropos
This is a program I had never heard of. You can use it to try and find a program that will do what you want.
$ apropos unzip
bunzip2 (1) - a block-sorting file compressor, v1.0.8
funzip (1) - filter for extracting from a ZIP archive in a pipe
gunzip (1) - compress or expand files
preunzip (1) - prefix delta compressor for Aspell
unzip (1) - list, test and extract compressed files in a ZIP archive
unzipsfx (1) - self-extracting stub for prepending to ZIP archives
file
This program will give you more info on a file.
$ file log.tar.gz
log.tar.gz: gzip compressed data, last modified: Sun Feb 14 19:43:28 2016, from Unix, original size modulo 2^32 2129920
stat
Gives file or file system status.
$ stat log.tar.gz
File: log.tar.gz
Size: 130340 Blocks: 256 IO Block: 4096 regular file
Device: fc03h/64515d Inode: 135200 Links: 1
Access: (0664/-rw-rw-r--) Uid: ( 1000/ pat) Gid: ( 1000/ pat)
Access: 2021-09-03 09:23:02.957218348 -0600
Modify: 2021-09-03 09:12:24.709826533 -0600
Change: 2021-09-03 09:12:24.709826533 -0600
Birth: 2021-09-03 09:12:24.709826533 -0600
cd
cd -
This one was mind blowing and another one of those ones that would have been good to know 10 years ago. This one moves back and fourth between current and previous directory
pat@pat-Standard-PC-Q35-ICH9-2009:~/commandlinebasics/Exercise Files$ cd -
/home/pat
pat@pat-Standard-PC-Q35-ICH9-2009:~$ cd -
/home/pat/commandlinebasics/Exercise Files
pat@pat-Standard-PC-Q35-ICH9-2009:~/commandlinebasics/Exercise Files$
sudo
The sudo -k will invalidate any cached credentials, the means the password
will need to be entered again on the next invocation. Wont use it often but
good to know.
sort
Haven't used this one much (ever?). This example sorts on column 2, numerically.
$ sort -k2 -n simple_data.txt
Name ID Team
Scott 314 Purple
Anne 556 Green
Miguel 671 Green
Ananti 991 Orange
Wes 1337 Orange
Jian 3127 Purple
sort -u only prints unique lines
Grand Finale
ip
And to top it all off.
ip a
Shows the ip address for all the networking adapters on the system. I have been
using ip addr show for years! So many wasted bits *smh.
So much left to learn
There is always so much to learn. Maybe I should dedicate 5-10 min a day to reading man pages. So many options that would have saved me so much typing over the years. It will be great to learn some of these "little" tricks from the pro training.