find

find . -type f -name "somefile.txt"   # finds files within current directory
      -iname    # will do case insensitive search
      -type d   # directories
find . -type f -mmin -10    # find files modified in the last 10m
      -mmin +10             # find files modified more than 10m ago
      -mtime -20 +5   # find files modified between 5-20 days ago
      -amin -atime  # access minutes | days
      -ctime  # changed min | days
      -size +5M # 5k=kilobytes | G=gigabytes
      -empty    # empty files
      -perm 755   # search files by permission

find some_dir -exec chown user:group {} +  # megacron:underlings
      # {} = placeholder for name since we are using find command (not giving a name)
      # + or \; is to end the -exec command
find some_dir -type d -exec chmod 775 {} +  # recursivly change perm on all dir in dir
find some_dir -type d -exec chmod 775 {} +  # recursivly change perm on all files in dir
find . -type f -name "*.jpg"  # always run find command before using rm like this
      -maxdepth 1   # sets so find will not tunnel down subdirectories
find . -type f -name "*.jpg" -maxdepth 1 -exec rm {} +    # removes all jpg files of current directory
find . \( -size +8k -o -size 8k \) ! -name "TekThing*.txt"  # backslash keeps () symbols from being in search
find . ! \( -size +8k -o -size 8k \) -name "TekThing*.txt" # tekthing that is <8k

# rename files
sudo find . -name "*.txt" -exec rename 's/txt/TXT/g' {} \;    # s=substitute g-globally on the computer.
sudo find . -name "*.jpg" -exec rename 'y/A-Z/a-z/' {} +    # rename files from upper to lower case
find . -type f -name ".*" -exec rename 's/^\.//' {} +    # remove leading . ie make unhidden
for file in .[^.]*; do mv "$file" "${file#.}"; done     # remove leading . ie make unhidden if rename cmd doesn't work  
rename 's/ //' *.jpg    # removes any spaces in a name
rename 's/ /_/' *.jpg   # convert spaces to underscore

# print to a file
find . -name "*.txt" -fprint testfile.txt
find . -name "*.txt" > testfile.txt

# sort
find . -type d | sort

# find by user
find . -user megacron   # find all files owned by that user