tered, an attemptismadetodefine afunctionusing``-f foo=bar'', an attempt is made to assign avaluetoareadonlyvariable, an attemptismadetoassign a valuetoan array variable withoutusingthe compound assignment syntax (see Arrays above), oneofthe namesisnota valid shell variable name, an attempti...
$ unset x $ showvar $x is not set $ x=3 $ showvar $x is not set $ export x $ showvar $x = 3 $ x= ## in bash, reassignment doesn't remove a variable from the environment $ showvar $x is set but empty 注意 showvar不是一个 bash 命令,而是一个如清单 5-1 所示的脚本,...
# 每一句指令以换行或分号隔开：echo 'This is the first line'; echo 'This is the second line'# 声明一个变量：Variable="Some string"# 下面是错误的做法：Variable = "Some string"# Bash 会把 Variable 当做一个指令，由于找不到该指令，因此这里会报错。# 也不可以这样：Variable= 'Some string'# ...
Using the multiple variable assignment technique in Bash scripts can make our code look compact and give us the benefit of better performance, particularly when we want to assign multiple variables by the output of expensive command execution. For example, let’s say we want to assign seven vari...
You can assign data to a variable using the equals sign (=). The data you store in a variable can either be a string or a number. Let’s create a variable now on the command line: chapter_number=5 The variable name is on the left hand side of the equals sign, and the data whic...
declare +i num # Removes the integer attribute from `num`. You can now assign other attribute (E.g. a string) without any errors: num=hello To verify it, print the variable value: echo $num It should outputhello. Please note thatdeclare +i numremoves the integer attribute but does not...
echo '$Variable' # 当你赋值 (assign) 、导出 (export),或者以其他方式使用变量时,变量名前不加 $。 # 如果要使用变量的值, 则要加 $。 # 注意: ' (单引号) 不会展开变量(即会屏蔽掉变量)。 # 在变量内部进行字符串代换 echo ${Variable/Some/A} ...
BASHPID The process ID of the current Bash process. In some cases, this can differ from $$. BASH_ALIASES Associative array variable. Each element holds an alias defined with the alias command. Adding an element to this array creates a new alias; removing an element removes the corresponding...
Execute the command: $command_to_execute Executes the command stored in the variable 'command_to_execute'. In this case, it runs the "ls /new_dir" command, listing the contents of the directory /new_dir. Get the exit status code: exit_status=$? Captures the exit status code of the ...
In this example we declare simple bash variable and print it on the screen ( stdout ) with echo command. #!/bin/bash STRING="HELLO WORLD!!!" echo $STRING 1. 2. 3. Your backup script and variables: #!/bin/bash OF=myhome_directory_$(date +%Y%m%d).tar.gz ...