forestbaker

# Simple Bash Hash Generator
#
# Author: Chris Hager <[email protected]>
#
# Put the `hashgen` method in your `.functions` file and source it from your `.bash_profile`
#
# Usage: hashgen [type] [#chars]
#
# Optional argument `type`:
# 

forestbaker

start on runlevel [2345]
stop on runlevel [016]

respawn
respawn limit 10 10

kill signal INT
kill timeout 20
normal exit 0 TERM INT

forestbaker

declare -rx IFC='/sbin/ifconfig'

showips() {

NAMES=( $($IFC | egrep 'lo|eth|wlan|en' -A 1 | awk -F' ' '{print $1 }' | egrep -v 'inet|-|UP|RX|collisions' | sort -u) )

for i in "${NAMES[@]}"; do
   echo "$i has ip address: $($IFC | grep $i -A 1 | grep 'addr' | awk -F' ' '{print $2}' | awk -F':' '{print $2}')"
done

forestbaker

Check if BASH_ENV is empty
set umask 077
Reset $PATH and $IFS
ALWAYS - use absolute path names
Check return codes from system utilities.
Signify the end of the option list with --
Quote all command line parameters (e.g. "$1")
Check user input for shell metacharacters and garbage
Check user supplied pathnames (absolute/relative)
set shell option noclobber to avoid overwriting existing files

forestbaker

# diplay alphabetically sorted list of processes with open files
# 'file' means: regular file, directory, block special, character special, executing text reference, library, stream or network file (Internet socket, NFS file or UNIX domain socket)
lsof | awk '{print $1}' | sort -u

# display all files that apache2 has open
# 
lsof -c apache2 | less

forestbaker

# display a random number based on the number of lines in a file
echo $(($RANDOM%`grep -c '$' ~/.bash_history`))

# replace COMMAND to find all the libboost libraries it is using
lsof | grep 'COMMAND.*mem.*libboost'

# display contents of file without comments or empty lines, also removes "in-line" comments
# this is an example of a reason to NOT USE IN LINE COMMENTS
egrep -v '#|^$' /etc/mysql/my.cnf

forestbaker

# one line command below
ssh -X -o UserKnownHostsFile=/dev/null -o CheckHostIP=no -o StrictHostKeyChecking=no \
-i /Users/veryv/.ssh/google_compute_engine -A -p 22 [email protected] --

forestbaker

needs file descriptor and something like this
exec 10>$temp
<$temp>


#!/bin/bash - 

# track path & filename for tempfile
temp="./example.tmp"

forestbaker

# fast & efficient triple check:
# existence, directory, writable || or error and exit
[[ -e  $DIR && -d $DIR && -w $DIR ]]  || { echo >&2 "Unable to access $DIR - check directory path / permissions?" ; exit 1 ; }

# exists , file, readable
[[ -s  $FILE && -d $FILE && -r $FILE ]]  || { echo >&2 "Unable to access $FILE - check file path / permissions?" ; exit 1 ; }

# exists , file, writable
[[ -s  $FILE && -d $FILE && -w $FILE ]]  || { echo >&2 "Unable to access $FILE - check file path / permissions?" ; exit 1 ; }

forestbaker

# closure - defined by Peter Landin in 1964
# closure - a function, plus a pointer to that functions scope

# In programming languages, closures (also lexical closures or function closures) are a technique for 
# implementing lexically scoped name binding in languages with first-class functions.  Duh.

# Operationally, a closure is a record storing a function[a] together with an environment:[1] 

# A mapping associating each free variable of the function (variables that are used locally, but defined in an enclosing scope) 
# with the value or storage location to which the name was bound when the closure was created.