mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-25 00:06:47 +03:00
Merge pull request #1070 from deryni/avoid-ALL_CAPS-variables
[bash/en] Don't use ALL_CAPS variable names.
This commit is contained in:
commit
675ddfd99d
@ -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
|
||||
|
Loading…
Reference in New Issue
Block a user