this error message occurs everywhere. You get it when you try to read a file that does not exist, when you try to change to a directory that isn’t there, when you try to write to a file in a directory
If you can enter commands into the shell, you can write shell scripts (also known as Bourne shell scripts). A shell script is a series of commands written in a file; the shell reads the commands from the file just as it would if you typed them into a terminal. 如果你能在 shell 中...
An example of an environment variable is thePATHvariable. It specifiesdirectorieswhere the system searches for executables. To see a variable's value, use theecho commandorprintenv: echo $PATH To create a new variable, use the syntax below: VARIABLE_NAME=value If a variable has more than one...
Here's how to write an interactive script with an easy tool calledDialog. It asks the user to choose between a variable number of machines (depending on the configuration file) and, of course, the password. However, if the remote user is the same for both machines (which is normal if y...
This tutorial discusses the range of uses for the set command and how to effectively write Bash scripts to set up good environment options. Command Tracing With set -x in Bash By default, running the set command alone will return a list of the currently set variables and their values, inclu...
There are many advantages of using the HOME variable. You can always reach your home directory by only typing ' cd ' at the prompt, irrespective of which directory you are presently within. This would immediately transfer you to your HOME directory. Besides in case you write scripts that have...
We declared a variable in the last example, but we can also have the user set the value of a variable dynamically. For example, instead of just having the script sayHello, World!, we can make it ask for the name of the person calling the script, then output that name. We'll do thi...
Introduction to Shell Scripts(第 11 章 Shell 脚本简介 Shell 脚本简介) If you can enter commands into the shell, you can write shell scripts (also known as Bourne shell scripts). A shell script is a series of commands written in a file; the shell reads the commands from the file just ...
You can also use the printenv command to get the value of any environment variable. $printenv VAR Issues related to environment variables While defining environment variables in bash scripts, the common issues are related to the parent-child relation of shells. The solution to such issues is to...
This chapter is a guide to the Unix commands and utilities that will be referenced throughout this book. This is preliminary material, and you may ...