A running list of BASH commands, syntax, and environmental variables

This page will be updated with new concepts for each lecture.

Commands

Command/Program	Description	example/syntax
9/4/18 - Scripting, executable permissions/conventions.
chmod	Change the mode of a file or directory	`chmod MODE FILE`
		`chmod OCTAL-MODE FILE`
echo	“echo” values to the screen	`echo “string $varname”`
nano	Edit a file	`nano FILE`
rev	reverse input stream	`echo “abcd” \| rev`
touch	Update file modification time. Create file if necessary	`touch FILE`
tr	Translate or delete characters	`tr [SET1] [SET2]`
which	Location of an executable in your PATH	`which ls`
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9/11/18

Variable name	Description	example/syntax
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HOME	Your home directory. Same as tilde (`~`)	`/home/yourname`
PATH	Search path for executables.	`/bin:/usr/bin:$HOME/bin`
PS1	Your prompt string.	`[\h \w]`
PWD	Your current directory, same as `pwd`	`~/dev`
USER	Your login/account, same as `whoami`	`eid@colostate.edu`
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Keyword(s)/Operators	Description	Example
9/4/18 - Scripting, executable permissions/conventions.
`[ ]`	conditional	`[ -z “” ]`
`if,then,else,fi`	flow control	`if [ -z “” ]; then echo 'empty!'; else echo 'NOT empty!'; fi`
`test`	flow control	`test -z “”`
`&& \|\|`	boolean operators for flow control	`[ -z “” ] && echo 'empty!' \|\| echo 'NOT empty!`'
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`let`	arithmetic assignment	`a=1; let a=a+1;`
`$((expr))`	arithmetic expressions	`echo $((a+1))`
`while`	loop	`a=0; while [ $a -lt 10 ]; do echo $a; let a=a+1; done`
`for var in list`	loop	`for num in 1 2 3; do echo $num; done`
9/11/18