Merge pull request #1070 from deryni/avoid-ALL_CAPS-variables

[bash/en] Don't use ALL_CAPS variable names.
This commit is contained in:
Levi Bostian 2015-05-08 14:32:40 -05:00
commit 675ddfd99d

View File

@ -32,40 +32,40 @@ echo Hello world!
echo 'This is the first line'; echo 'This is the second line'
# Declaring a variable looks like this:
VARIABLE="Some string"
Variable="Some string"
# But not like this:
VARIABLE = "Some string"
# Bash will decide that VARIABLE is a command it must execute and give an error
Variable = "Some string"
# Bash will decide that Variable is a command it must execute and give an error
# because it can't be found.
# Or like this:
VARIABLE= 'Some string'
Variable= 'Some string'
# Bash will decide that 'Some string' is a command it must execute and give an
# error because it can't be found. (In this case the 'VARIABLE=' part is seen
# error because it can't be found. (In this case the 'Variable=' part is seen
# as a variable assignment valid only for the scope of the 'Some string'
# command.)
# Using the variable:
echo $VARIABLE
echo "$VARIABLE"
echo '$VARIABLE'
echo $Variable
echo "$Variable"
echo '$Variable'
# When you use the variable itself — assign it, export it, or else — you write
# its name without $. If you want to use variable's value, you should use $.
# Note that ' (single quote) won't expand the variables!
# String substitution in variables
echo ${VARIABLE/Some/A}
echo ${Variable/Some/A}
# This will substitute the first occurance of "Some" with "A"
# Substring from a variable
LENGTH=7
echo ${VARIABLE:0:LENGTH}
Length=7
echo ${Variable:0:Length}
# This will return only the first 7 characters of the value
# Default value for variable
echo ${FOO:-"DefaultValueIfFOOIsMissingOrEmpty"}
# This works for null (FOO=) and empty string (FOO=""); zero (FOO=0) returns 0.
echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"}
# This works for null (Foo=) and empty string (Foo=""); zero (Foo=0) returns 0.
# Note that it only returns default value and doesn't change variable value.
# Builtin variables:
@ -78,12 +78,12 @@ echo "Scripts arguments seperated in different variables: $1 $2..."
# Reading a value from input:
echo "What's your name?"
read NAME # Note that we didn't need to declare a new variable
echo Hello, $NAME!
read Name # Note that we didn't need to declare a new variable
echo Hello, $Name!
# We have the usual if structure:
# use 'man test' for more info about conditionals
if [ $NAME -ne $USER ]
if [ $Name -ne $USER ]
then
echo "Your name isn't your username"
else
@ -95,14 +95,14 @@ echo "Always executed" || echo "Only executed if first command fails"
echo "Always executed" && echo "Only executed if first command does NOT fail"
# To use && and || with if statements, you need multiple pairs of square brackets:
if [ $NAME == "Steve" ] && [ $AGE -eq 15 ]
if [ $Name == "Steve" ] && [ $Age -eq 15 ]
then
echo "This will run if $NAME is Steve AND $AGE is 15."
echo "This will run if $Name is Steve AND $Age is 15."
fi
if [ $NAME == "Daniya" ] || [ $NAME == "Zach" ]
if [ $Name == "Daniya" ] || [ $Name == "Zach" ]
then
echo "This will run if $NAME is Daniya OR Zach."
echo "This will run if $Name is Daniya OR Zach."
fi
# Expressions are denoted with the following format:
@ -171,7 +171,7 @@ echo "There are $(ls | wc -l) items here."
echo "There are `ls | wc -l` items here."
# Bash uses a case statement that works similarly to switch in Java and C++:
case "$VARIABLE" in
case "$Variable" in
#List patterns for the conditions you want to meet
0) echo "There is a zero.";;
1) echo "There is a one.";;
@ -179,10 +179,10 @@ case "$VARIABLE" in
esac
# for loops iterate for as many arguments given:
# The contents of $VARIABLE is printed three times.
for VARIABLE in {1..3}
# The contents of $Variable is printed three times.
for Variable in {1..3}
do
echo "$VARIABLE"
echo "$Variable"
done
# Or write it the "traditional for loop" way:
@ -193,16 +193,16 @@ done
# They can also be used to act on files..
# This will run the command 'cat' on file1 and file2
for VARIABLE in file1 file2
for Variable in file1 file2
do
cat "$VARIABLE"
cat "$Variable"
done
# ..or the output from a command
# This will cat the output from ls.
for OUTPUT in $(ls)
for Output in $(ls)
do
cat "$OUTPUT"
cat "$Output"
done
# while loop:
@ -230,7 +230,7 @@ bar ()
}
# Calling your function
foo "My name is" $NAME
foo "My name is" $Name
# There are a lot of useful commands you should learn:
# prints last 10 lines of file.txt