forestbaker

#!/usr/bin/env bash
# From Bash Hackers - http://wiki.bash-hackers.org/howto/collapsing_functions
# The first time you run chatter(), the function redefines itself based on the value of verbose. Thereafter, chatter doesn't check $verbose, it simply is.
# Further calls to the function reflect its collapsed nature. 
# If verbose is unset, chatter will echo nothing, with no extra effort from the developer.

[[ $1 = -v || $1 = --verbose ]] && verbose=1

chatter() {
  if [[ $verbose ]]; then

forestbaker

# for loop on directories in PATH 
for foo in ${PATH//:/ }; do

done

# use mapfile to load binaries
# just loads up element 0
mapfile _binary <${PATH//:/\/\* }

forestbaker

Complex Shell Script Outline
----------------------------
header
begin script
preamble:
 - sanity checks
 - create shell environ
 - log & debug
error handling
check dependencies

forestbaker

http://www.kfirlavi.com/blog/2012/11/06/elegant-locking-of-bash-program/

Simple
#########################################
#!/bin/bash

# exit if flock fails.
set -e

# Wait for lock on /var/lock/.myscript.exclusivelock (fd 200) for 10 seconds

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. 

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

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


#!/bin/bash - 

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

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

# 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

# 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