my cheat bash (both linux and mac osx)…

EDITOR=/user/local/bin/emacs

echo $EDITOR

You can use either single or double quoatation marks (tics or dirks). When you use dirks, any variable reference inside the dirks get expanded. When you use tics, the variable is treated not as a variable but as a literal string.

echo "My editor is $EDITOR"
echo 'My editor is $EDITOR'

Results in this output:

My editor is /usr/local/bin/emacs
My editor is $EDITOR

It is very easy to convert a string to upper or lower case in bash. the ,, and ^^ operators do it as shown in this example:

a = "Hello World"
echo $a        # will show "Hello World"
echo "${a}"    # will show "Hello World"
echo "${a,,}"   # will show "hello world"
echo "${a^^}"   # will show "HELLO WORLD"

Notice, that this works on my Linux bash shell, but does NOT work on my darwin mac osx bash shell. I get a bash: ${a^^}: bad substitution error. That is because my Linux is running BASH 4.0 (4.4.20(1) actually) where my macbook pro is running BASH 3.2.57(1)

For my macbook I can do this: (courtesy of stackoverflow.com )

A couple of reserved variables that are useful:

$? is the error code

function myinfo {
  printf "\n"
  uname -a | awk '{ printf "Kernel: %s " , $3 }'
  uname -m | awk '{ printf "%s | " , $1 }'
  printf "\n"
  uptime | awk '{ printf "Uptime: %s %s %s", $3, $4, $5 }' | sed 's/,//g'
  printf "\"
}

To use this later, just type myinfo()

for file in *.org
   sed 's/zintis AT gmail DOT com/zintis AT senecacollege DOT ca/' $file > $file.new
end

check the results and if good:

for file in *.org.new
   mv "$file" "{$file%.new}.old"
end

A common find command to list directories: find . -maxdepth 1 -type d -print I can put that into a for loop to do something in each of these directories.

for d in $(find /path/to/dir -maxdepth 1 -type d)
do
  #Do something, the directory is accessible with $d:
  echo $d
done > output_file

Here is a concrete example I use when moving my html files to a target dir;

for d in $(find ~/eg -maxdepth 1 -type d)
do
  mv $d/*.html ~/Documents/visada/exported-html
  echo $d
done

can use cd - to change to the previous directory

You can also use $OLDPWD, which is the old directory. That is always maintained by bash, so you can use it in scripts, or make an alias using cd $OLDPWD.

Just like in Linux bash

To copy files and directories (duplicating them) you can use -V option for "verbose" and the command: ditto -V /src-dir /dest-dir For files it is ditto -V /src-dir/top-gun.mp4 /dest-dir

Makes common spelling corrections when using cd. So cd ~/Desktpo will actually catch the error and cd you to ~/Desktop

If a command is not a valid command, autocd will check if the command is actaully the name of a directory, and if it is, will cd to that directory.

If I add export CDPATH=/Users/zintis/bin/python to my .bash_profile bash will check a matching directory in that path 1st and if a match is found, will cd into that directory, saving you from having to type cd ~/bin/python/bin instead letting you type cd bin

I can still cd into the absolute path, for example cd /usr/bin, but if I was in /usr then cd bin would NOT put me in /usr/bin but ~/bin/python/bin

Otherwise pretty useful if you spend a lot of time in ~/bin/python

defaults write com.apple.finder _FXShowPosixPathInTitle -boolean true This is entered via terminal, but really is for the finder gui windows.

defaults write com.apple.screencapture location ~/Downloads

defaults write com.apple.dashboard mcx-disabled -boolean TRUE

To download a file given an http url: curl -O

caffeinate -u -t 3600 won't sleep for 1 hour (3600 seconds) caffeinate won't sleep at all

obvious

Assume you have a file called junk1 in a directory /x/y/z, so /x/y/z/junk1

1. cd to a target directory that does not contain a file called junk1 cd /usr/local/bin
2. ln -s /x/y/z/junk1 will create a link in /usr/local/bin, namely: /usr/local/bin/junk1 -> /x/y/z/junk1
3. The second form, in the /x/y/z directory: ln -s junk1 junk2 will create a link in /x/y/z/junk2 -> /x/y/z/junk1

In the manual pages, i.e. man ln target means the new symbolic link which in my mind is opposite. Just be ware of that.

ln -s existing-file target-directory or ln -s existing-file new-pointer-to-existing-file ln -s existing-file symb-link-to-existing-file

so, for me this creates:

• new-pointer-to-existing-file -> existing file (kind of the reverse order that these were entered into the ln -s command)

Zintiss-MacBook-Pro-5:~] zintis% ln -s CAN-pricelist.txt pricelist

[Zintiss-MacBook-Pro-5:~] zintis% lst
total 207296
-rw-r--r--@   1 zintis  staff  45580288  4 Jan 10:44 CAN-pricelist.txt
lrwxr-xr-x    1 zintis  staff        17  4 Jan 10:44 pricelist -> CAN-pricelist.txt
drwx------+ 133 zintis  staff      4522  4 Jan 10:36 Documents
drwx------+  22 zintis  staff       748  4 Jan 10:28 Downloads

• ln -s source-file target-directory

Given one or two arguments, ln creates a link to an existing file source_file. If target_file is given, the link has that name; target_file may also be a directory in which to place the link; otherwise it is placed in the current directory. If only the directory is speci- fied, the link will be made to the last component of source_file.

So to get ~/Movies to point to an external drive do the following:

cd to ~/
ln -s /Volumes/WD-3TB-perkons/Movies/ Movies

then still in ~/ directory run:

ls -l 

and you'll see:

[Zintiss-MacBook-Pro-2:~] zintis% pwd
/Users/zintis
[Zintiss-MacBook-Pro-2:~] zintis% ls -l
.
.
.
drwx------+ 143 zintis  staff      4862 25 Jun 13:31 Documents
drwx------+  41 zintis  staff      1394 28 Jun 13:04 Downloads
drwx------@  58 zintis  staff      1972 13 May 10:38 Library
lrwxr-xr-x    1 zintis  staff        31 30 Jun 13:40 Movies -> /Volumes/WD-3TB-perkons/Movies/
drwx------+   7 zintis  staff       238 31 Mar 22:27 Music
drwxr-xr-x    4 zintis  staff       136 30 Aug  2011 NetApp
drwx------+ 103 zintis  staff      3502  3 May 13:57 Pictures
drwxr-xr-x+   6 zintis  staff       204 22 Aug  2011 Public
.
.
.

An example with output:

mkdir /Users/Shared/Pictures/iPhoto\ Library

sudo ln -s /Users/Shared/Pictures/iPhoto\ Library/ /Users/user1/Pictures/iPhoto\ Library

sudo ln -s /Users/Shared/Pictures/iPhoto\ Library/ /Users/user2/Pictures/iPhoto\ Library

Output:

cd /Volumes
[rtp-zperkons-8717:/Volumes] zintis% pwd
/Volumes
[rtp-zperkons-8717:/Volumes] zintis% ls -la
total 24
drwxrwxrwt@  6 root    admin   204  9 Dec 00:19 .
drwxr-xr-x  33 root    wheel  1190  9 Dec 01:36 ..
-rw-r--r--@  1 zintis  admin  6148 25 Sep 21:07 .DS_Store
lrwxr-xr-x   1 root    admin     1  7 Dec 09:27 320GB-HItachi -> /
drwxrwxrwx   0 root    wheel     0  9 Dec 11:43 MobileBackups
drwxrwxr-x  25 zintis  staff  1326  9 Dec 11:23 WD-3TB-perkons
[rtp-zperkons-8717:/Volumes] zintis% ln -s WD-3TB-perkons/ WD-1TB-partition
[rtp-zperkons-8717:/Volumes] zintis% ls -la
total 32
drwxrwxrwt@  7 root    admin   238  9 Dec 12:04 .
drwxr-xr-x  33 root    wheel  1190  9 Dec 01:36 ..
-rw-r--r--@  1 zintis  admin  6148  9 Dec 12:04 .DS_Store
lrwxr-xr-x   1 root    admin     1  7 Dec 09:27 320GB-HItachi -> /
drwxrwxrwx   0 root    wheel     0  9 Dec 11:43 MobileBackups
lrwxr-xr-x   1 zintis  admin    15  9 Dec 12:04 WD-1TB-partition -> WD-3TB-perkons/
drwxrwxr-x  25 zintis  staff  1326  9 Dec 11:23 WD-3TB-perkons
[rtp-zperkons-8717:/Volumes] zintis% 

And from ln man pages:

SYNOPSIS
     ln [-Ffhinsv] source_file [target_file]
     ln [-Ffhinsv] source_file ... target_dir
     link source_file target_file

-s    Create a symbolic link.

 By default, ln makes hard links.  A hard link to a file is indistinguishable
 from the original directory entry; any changes to a file are effectively
 independent of the name used to reference the file.  Hard links may not nor-
 mally refer to directories and may not span file systems.

 A symbolic link contains the name of the file to which it is linked.  The
 referenced file is used when an open(2) operation is performed on the link.
 A stat(2) on a symbolic link will return the linked-to file; an lstat(2)
 must be done to obtain information about the link.  The readlink(2) call may
 be used to read the contents of a symbolic link.  Symbolic links may span
 file systems and may refer to directories.

 Given one or two arguments, ln creates a link to an existing file
 source_file.  If target_file is given, the link has that name; target_file
 may also be a directory in which to place the link; otherwise it is placed
 in the cur- rent directory.  If only the directory is specified, the link
 will be made to the last component of source_file.

 Given more than two arguments, ln makes links in target_dir to all the named
 source files.  The links made will have the same name as the files being
 linked to.

Call tput as part of a sequence of commands:

tput setaf 1; echo "this is red text"

Use ; instead of && so if tput errors, the text still shows.

Another option is to use shell variables:

• red=`tput setaf 1`
• green=`tput setaf 2`
• reset=`tput sgr0`
• echo "${red}red text \({green}green text\){reset}"

tput produces character sequences that are interpreted by the terminal as having a special meaning. They will not be shown themselves. Note that they can still be saved into files or processed as input by programs other than the terminal.

#!/bin/bash
RED='\033[0;31m'
YELLOW='\033[1;33;40m'
NC='\033[0m' # No Color
RED=`tput setaf 1`
GREEN=`tput setaf 2`
YELLOW=`tput setaf 3`
BLUE=`tput setaf 4`
MAGENTA=`tput setaf 5`
CYAN=`tput setaf 6`
WHITE=`tput setaf 6`
printf "Here is ${RED}red${NC} and here is ${YELLOW}yellow${NC}\n"
echo " "
echo " Showing what python, python2, and python3 would be running based on"
echo " environment variables set as shown: "
echo "--------------------------------- "

for x in python python2 python3; do
    echo "${CYAN}"; which $x
    echo "${YELLOW}"; readlink $(which $x)
    echo "${MAGENTA}";$x --version
    echo "-----------------------------------"
done

echo ""
echo "  Current values of environment variables:"
echo "           PATH is  $PATH"
echo "  PYENV_VERSION is $PYENV_VERSION"
echo ""
echo ""

#!/bin/bash
## brew uninstall --force --ignore-dependencies python python2 python2.7 python3 python3.6 > /dev/null 2>&1
## brew install python@2 python@3 > /dev/null 2>&1
RED='\033[0;31m'
YELLOW='\033[1;33;40m'
NC='\033[0m' # No Color
RED=`tput setaf 1`
GREEN=`tput setaf 2`
YELLOW=`tput setaf 3`
BLUE=`tput setaf 4`
MAGENTA=`tput setaf 5`
CYAN=`tput setaf 6`
WHITE=`tput setaf 6`
printf "I ${RED}love${NC} Stack Overflow\n"
echo " "
echo " Showing what python, python2, and python3 would be running based on"
echo " environment variables set as shown: "
echo "--------------------------------- "
echo "${CYAN} done"
for x in python python2 python3; do
    which $x
    readlink $(which $x)
    $x --version
    echo "-----------------------------------"
done

echo ""
echo "  Current values of environment variables:"
echo "           PATH is  $PATH"
echo "  PYENV_VERSION is $PYENV_VERSION"
echo ""
echo ""
alias taka='tput setaf 5;echo -e "${PURPLE}${PATH//:/\\n}"'