Cheat is from http://cheat.sh and it is my favorit.

Put this in your .bashrc or .zshrc file.
function cs() { curl -m 7 "http://cheat.sh/$1"; }

Exsamples: 3

$> cs perl/for
# Which "for" loop to use in Perl?
#
# In your case, there's no difference.
#
# In other use cases, in a for-each loop you don't have control of /
# access to the iterator.
#
# Editing to try and make this clearer:
#
# Using your example syntax:

for my $i (0..10)
{
   print "$i";
   $i++;
}

# The above actually creates a foreach loop - it's the same as saying
# foreach my $i (0..10). $i is a value returned from the list, not the
# iterator. The iterator is internal and you have no access to it; you
# can not control the flow of the loop.
#
# The output from above will print 012345678910
#
# This:

for ( my $i = 0; $i++ ; $i <= 10)
{
    print $i;
    $i++;
}

# That is an actual for loop. You are controlling and outputting the
# iterator. It will output:
# 0246810
#
# Edit: In addition:
#
# When you do for (1..$n) you are invoking the range operator
# (http://perldoc.perl.org/perlop.htmlRange-Operators) vs. doing a
# simple comparison at the top of the loop. Performance differences,
# however, would be immeasurable.
#
# [Brian Roach] [so/q/5757345] [cc by-sa 3.0]

~
$> cs zsh/for
# shell - ZSH for loop array variable issue
#
# It's actually much simpler than that:

lw=('plugin1' 'plugin2' 'plugin3')

for i in $lw; do
  . ~/Library/Rogall/plugins/$i/lw.prg end
done

# In summary:
#
    # * Assign to "foo", not "$foo" (the shell would try to expand $foo
# and assign to whatever it expands to; typically not useful)
    # * Use the loop variable directly; it contains the array value
# rather than the index
#
# [Jan Kr&252;ger] [so/q/10887560] [cc by-sa 3.0]

$> cs grep
 cheat:grep
# To search a file for a pattern:
grep <pattern> <file>

# To perform a case-insensitive search (with line numbers):
grep -in <pattern> <file>

# To recursively grep for string <pattern> in <dir>:
grep -R <pattern> <dir>

# Read search patterns from a file (one per line):
grep -f <pattern-file> <file>

# Find lines NOT containing pattern:
grep -v <pattern> <file>

# To grep with regular expressions:
grep "^00" <file>                                               # Match lines starting with 00
grep -E "[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}" <file> # Find IP add

# To find all files that match <pattern> in <dir>
grep -rnw <dir> -e <pattern>

# To exclude grep from your grepped output of ps:
# (Add [] to the first letter. Ex: sshd -> [s]shd)
ps aux | grep '[h]ttpd'

# Colour in red {bash} and keep all other lines
ps aux | grep -E --color 'bash|$'