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What Is syntax for select loop?
The select loop syntax is very close to the one of a for loop: select name [in words …]; do commands; done . If a number is provided by the user, then the name variable from the select loop is set to the corresponding word (menu item). Any other value read causes name to be set to null.
How do you write a loop in a shell script?
Look at the above syntax:
- Keywords are for, in, do, done.
- List is a list of variables which are separated by spaces. If list is not mentioned in the for statement, then it takes the positional parameter value that were passed into the shell.
- Varname is any variable assumed by the user.
How do you select in Unix?
select command in Linux is used to create a numbered menu from which a user can select an option. If the user enters a valid option then it executes the set of command written in select block and then ask again to enter a number, if a wrong option is entered it does nothing.
What is the looping?
In computer programming, a loop is a sequence of instruction s that is continually repeated until a certain condition is reached. Typically, a certain process is done, such as getting an item of data and changing it, and then some condition is checked such as whether a counter has reached a prescribed number.
How to run select loop in Bash shell?
The Bash Shell also offer select Loop, the syntax is: Select command use PS3 variable to print its prompt. Each word in list is printed on screen preceded by a number. If the line consists of the number corresponding to one of the displayed words (from the list), then varName is set to that word.
Is the Select Loop part of the for loop?
Despite its name, the select loop is not part of the bash loop constructs. Like the bash if keyword, the select keyword is part of the conditional constructs in the bash manual. The select loop syntax is very close to the one of a for loop: select name [in words …]; do commands; done.
What does done mean in Bash for loop?
The part $ {file// /_} is using the shell parameter expansion to replace a pattern within a parameter with a string. done indicates the end of the loop segment. The following example shows how to use the Bash for loop to rename all files ending with .jpeg in the current directory by replacing the file extension from .jpeg to .jpg.
Below is an example using the bash select loop to generate a selectable menu from a bash array, using the PS3 variable to set the user prompt, and displaying the menu and index selected. The menu display a list of animal and object and prompt the user to select one.