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{{Admon/tip|Bash Shell Scripting Tips:|<br><ul><li>'''Data Input:'''<br><br>A shell script can obtain data from a number of methods: '''reading input files''', using '''arguments when issuing command''' (positional parameters), or '''prompting for data to store in a variable'''. The later method can be accomplished by using the '''read''' command, for example: '''read -p "Enter your name: " userName'''.<br><br></li><li>'''Mathematical Expressions:'''<br><br>In shell scripting, data is stored in variable as text, not other data types (ints, floats, chars, etc) like in compiled programs like C or Java. In order to have a shell script perform '''mathematical operations''', number or variable need to be surrounded by two sets of parenthesis '''((..)) ''' in order to convert a number stored as text to a binary number.<br><br><u>'''Examples'''</u><br><br>''var1=5;var2=10''<br>''echo "$var1 + $var2 = $((var1+var2))"''<br><br'''>Note:''' shell does not perform floating point calculations (like 5/10). Instead, other commands like '''awk''' or '''bc''' would be required for floating point calculations (decimals)<br><br></li><li>'''Loops (iteration):'''<br><br>x<br><br>'''<u>Examples (try in a shell script)</u>'''<br><br>''set ops235 is fun''<br>''for x''<br>''do''<br> ''echo "argument is $x"''<br>''done''<br><br>''for x in $(ls)''<br>''do''<br> ''echo "Filename: $x"''<br>''done''<br><br>''read -p "enter a whole number: " num''<br>''until echo $num | grep -q "^[0-9][0-9]*$"''<br>''do''<br> ''read -p "Incorrect. Please enter WHOLE NUMBER: " num''<br>''done''<br><br></li></ul>}}
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