diff options
| -rw-r--r-- | bash.html.markdown | 86 |
1 files changed, 44 insertions, 42 deletions
diff --git a/bash.html.markdown b/bash.html.markdown index c9a805ba..4ab800a4 100644 --- a/bash.html.markdown +++ b/bash.html.markdown @@ -18,6 +18,7 @@ contributors: - ["Harry Mumford-Turner", "https://github.com/harrymt"] - ["Martin Nicholson", "https://github.com/mn113"] - ["Mark Grimwood", "https://github.com/MarkGrimwood"] + - ["Emily Grace Seville", "https://github.com/EmilySeville7cfg"] filename: LearnBash.sh translators: - ["Dimitri Kokkonis", "https://github.com/kokkonisd"] @@ -37,67 +38,68 @@ or executed directly in the shell. # As you already figured, comments start with #. Shebang is also a comment. # Simple hello world example: -echo Hello world! # => Hello world! +echo "Hello world!" # => Hello world! # Each command starts on a new line, or after a semicolon: -echo 'This is the first line'; echo 'This is the second line' -# => This is the first line -# => This is the second line +echo "This is the first command"; echo "This is the second command" +# => This is the first command +# => This is the second command # Declaring a variable looks like this: -Variable="Some string" +variable="Some string" # But not like this: -Variable = "Some string" # => returns error "Variable: command not found" -# Bash will decide that Variable is a command it must execute and give an error +variable = "Some string" # => returns error "variable: command not found" +# Bash will decide that `variable` is a command it must execute and give an error # because it can't be found. # Nor like this: -Variable= 'Some string' # => returns error: "Some string: command not found" -# 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 -# as a variable assignment valid only for the scope of the 'Some string' -# command.) +variable= "Some string" # => returns error: "Some string: command not found" +# 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 +# as a variable assignment valid only for the scope of the "Some string" +# command. # Using the variable: -echo $Variable # => Some string -echo "$Variable" # => Some string -echo '$Variable' # => $Variable +echo "$variable" # => Some string +echo '$variable' # => $variable # When you use the variable itself — assign it, export it, or else — you write # its name without $. If you want to use the variable's value, you should use $. # Note that ' (single quote) won't expand the variables! - -# Parameter expansion ${ }: -echo ${Variable} # => Some string -# This is a simple usage of parameter expansion -# Parameter Expansion gets a value from a variable. -# It "expands" or prints the value -# During the expansion time the value or parameter can be modified -# Below are other modifications that add onto this expansion - -# String substitution in variables -echo ${Variable/Some/A} # => A string -# This will substitute the first occurrence of "Some" with "A" - -# Substring from a variable -Length=7 -echo ${Variable:0:Length} # => Some st +# You can write variable without surrounding quotes but it's not recommended. + +# Parameter expansion ${...}: +echo "${variable}" # => Some string +# This is a simple usage of parameter expansion such as two examples above. +# Parameter expansion gets a value from a variable. +# It "expands" or prints the value. +# During the expansion time the value or parameter can be modified. +# Below are other modifications that add onto this expansion. + +# String substitution in variables: +echo "${variable/Some/A}" # => A string +# This will substitute the first occurrence of "Some" with "A". + +# Substring from a variable: +length=7 +echo "${variable:0:length}" # => Some st # This will return only the first 7 characters of the value -echo ${Variable: -5} # => tring -# This will return the last 5 characters (note the space before -5) +echo "${variable: -5}" # => tring +# This will return the last 5 characters (note the space before -5). +# The space before minus is mandatory here. -# String length -echo ${#Variable} # => 11 +# String length: +echo "${#variable}" # => 11 -# Indirect expansion -OtherVariable="Variable" -echo ${!OtherVariable} # => Some String -# This will expand the value of OtherVariable +# Indirect expansion: +other_variable="variable" +echo ${!other_variable} # => Some string +# This will expand the value of `other_variable`. -# Default value for variable -echo ${Foo:-"DefaultValueIfFooIsMissingOrEmpty"} +# Default value for variable: +echo "${foo:-"DefaultValueIfFooIsMissingOrEmpty"}" # => DefaultValueIfFooIsMissingOrEmpty -# This works for null (Foo=) and empty string (Foo=""); zero (Foo=0) returns 0. +# 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. # Declare an array with 6 elements |