Handy for getting the date, but you can also format it and include it the output when renaming things.

snippet.bash

DATE=$(date +%Y%m%d)

You can compare two directories using…

snippet.bash

diff --brief -r dir1/ dir2/

Diffing on two different systems

I'm forever forgetting how to use find so have written down examples I found from here.

snippet.bash

# Find files of name blah in / (ignores case)
find / -iname blah
# Find files of name blah in / (case sensitive)
find / -name blah
# Find directories of name blah in /home
find /home -type d -name blah
# Find files using glob
find /home -type f -name "*.txt"
# Permissions 777
find / -type f -perm 0777 -print
# Without Permissions 777
find / -type f ! -perm 0777 -print
# File based on user
find /home -user blah
# File based on group
find /home -group blah
# Modified in the last 50 days
find / -mtime 50
# Accessed in the last 50 days
find / -atime 50
# Modified last 50-100 days
find -mtime +50 -mtime -100
# Modified in last hour
find / -mmin -60
# Files based on size
find / -szie +50M -size -100M

Will rename files using an sed like syntax. For example to lowercase all file names

snippet.bash

rename 'y/A-Z/a-z/' *

Generate the md5 (or otherwise) checksum for all files under a given directory

snippet.bash

# md5 sum for all files in the current directory, following symbolic links (-L)
find -L . -type f -exec md5sum '{}' \; > ~/checksum_of_files.md5

If you don't have you ~/.ssh/config set up to define the port for the target then you sometimes have to specify this on the command line call to rsync.

snippet.bash

rsync -av  -e 'ssh -p 2222' * target:~/tmp/.

Put a list of the files you want to copy in a file and use --from-file=FILE

snippet.bash

rsync -av --from-file=some_files_to_copy.txt ~/ remote:~/tmp/.

sort is a very useful utility, not only does it do what it says on the tin but it can also reduce a list of rows to unique observations with the -u flag.

You can look at the contents of a tar ball without extracting them using…

snippet.bash

tar -ztf some.tar.gz

Counts characters, words and lines, very handy.

snippet.bash

# Count number of files in a directory
ls -l | grep -v '^total' |  wc -l

Useful for downloading web-pages and files.

snippet.bash

# -nd prevents creation of directory hierarchy
# -r recursive download
# -A only get items with specified extension
wget -nd -r -A jpg,jpeg,png,mp3 http://djriko.com/mixmases.htm

This happens on occasions and there are some ways around it as explained here.