Command Line JivePublished on 5 September 2013 by Amanda
Caveats: # <-- This is the root command prompt. It means run as root (or use sudo). I often tend to be too cavalier to just be one of those sudo pussies! $ <-- This is the unprivileged command prompt. It means run as an unprivileged user, like you. [new group] [user] <-- These are not regular expressions [D|d] [0-9][G] <-- These are regular expressionsRedirecting input/output:
stdin - 0 - Standard Input (usually keyboard or file)
stdout - 1 - Standard Output (usually screen)
stderr - 2 - Standard Error (usually screen)
ex.: command 2> /dev/null redirects error messages to special device /dev/null
Scale a video with ffmpeg:
$ ffmpeg -i ./input.mp4 -vf scale=640:360 $HOME/Videos/output.mp4
How to hold a package at a specific version:
sudo apt-mark hold package_name
$ shred -n 32 -v -u -z
Generate random character strings:
$ cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 10 | head -n 10The tr command constrains output to alphanumeric characters.
The fold command creates strings 10 columns wide.
The head command creates 10 strings.
Create a CDROM ISO from a directory on a hard drive:
$ mkisofs -J -r -o [output.iso] [directory to be burned]
Get some info about a CD-ROM:
$ isoinfo -d -i /dev/sr0
Create an ISO using info from isoinfo:
$ dd if=/dev/sr0 bs=blocksize count=count of=/path/to/isoimage.iso
Get some information about an ISO image:
$ isoinfo -d -i /apps/images/wxpvol_en.iso
Here, play with that...
$ echo $(( `date +%Y` - 1964 ))
$ rsync -rvbpogt root@fembot:/apps/backups /mnt/external/
Where: -r recursive -v verbose -p preserve permissions -o preserve owner -g preserve group -t preserve time All I ever really use is rsync -rac --progress [...]addgroup quickie
# addgroup -gid [New Group Number] [group name]
This will append [group name] to the list of groups [user] is a member of. The -a is significant. ALL GROUPS the user currently belongs to will be clobbered (removed from the user's group membership list) without it. For example, my current group membership is: amanda adm dialout cdrom plugdev lpadmin admin sambashare allaccess. Without the -a my group membership will be changed to only: [group name], whish is bad.
# usermod -a -G [group name] [user]
This will find directories that are x GB in size. Where: [-h] is human-readable (12 GB instead of 12010400)
$ du -h | grep [0-9][G]
This will find lines in a file that start with the letter s and end with the letter n:
$ grep '^s.*n$' myfile
This will find lines in a file that start with either the letter R or c and end with the letter N:
$ grep '^[R,c].*N$' myfile
This will search recursively, print the file name and line number, and match whole string/word:
grep -rnw '/path/to/somewhere/' -e 'pattern'
Finding unused kernels on the system with sed:
$ ls /boot/ | grep vmlinuz | sed 's@vmlinuz-@linux-image-@g' | grep -v `uname -r`
Using checkinstall to compile and install packages.
sudo checkinstall --pkgname=ncmpcpp-x86 --pkgversion="0.7" --backup=no --default --deldoc=yes