- Tcl/Tk 8.5 Programming Cookbook
- Copyright
- Credits
- About the Author
- Acknowledgment
- About the Reviewers
- www.PacktPub.com
- Preface
- 1. The Tcl Shell
- 2. Using the Building Blocks Control Constructs
- 3. Error Handling
- 4. Handling String Expressions
- Introduction
- Appending to a string
- Formatting a string
- Matching a regular expression within a string
- Performing character substitution on a string
- Parsing a string using conversion specifiers
- Determining the length of a string
- Comparing strings
- Comparing a string of characters
- Locating the first instance of a character
- Locating the index of a character
- Determining the class of a string
- Locating the last instance of a string
- Determining the size of a string
- Replacing values within a string
- Locating a pattern within a string
- Returning a range of characters from a string
- Creating a string of repeated characters
- Replacing ranges of characters contained within a string
- Creating a reverse string
- Converting a string to lowercase
- Converting a string to title
- Converting a string to uppercase
- Trimming a string
- Trimming leading whitespace
- Trimming trailing whitespace
- Locating the word end
- Locating the word start
- Performing variable substitution
- 5. Expanding String Functionality Using Lists
- Introduction
- Creating a list
- Joining two lists
- Joining list elements
- Appending list elements
- Assigning list elements to variables
- Retrieving an element from a list
- Inserting elements into a list
- Determining the number of elements
- Getting a list element
- Repeating elements
- Replacing elements
- Reversing elements
- Searching a list
- Editing a list
- Sorting a list
- Splitting a string into a list
- 6. The Tcl Dictionary
- Introduction
- Creating a dictionary
- Appending to a dictionary
- Determining if a key exists
- Filtering a dictionary
- Searching a dictionary
- Getting a record
- Incrementing a value
- Getting the dictionary structure
- Getting a list of keys
- Appending to an existing record
- Merging two dictionaries
- Creating a blank dictionary structure
- Updating variables from a dictionary
- Determining the size of a dictionary
- Getting all records
- Assigning values
- 7. File Operations
- 8. Tk GUI Programming with Tcl/Tk
- 9. Configuring and Controlling Tk Widgets
- 10. Geometry Management
- 11. Using Tcl Built-in Dialog Windows
- 12. Creating and Managing Menus
- 13. Creating the Address Book Application
When writing a program, there is no way to ensure that only correctly formatted data is provided. An end-user may inadvertently enter whitespace, a test file may contain whitespaces, and so on. To address this issue, Tcl provides keywords to trim the undesirable whitespaces or characters if specified. The first of these is the trim keyword.
The syntax of the string command is as follows:
string trim string characters
If no characters are provided, the trim keyword will return the string with all leading and trailing whitespace trimmed. If the characters are not specified (specifying the characters is optional), only those whitespaces will be removed.
In the following example, we will trim the .gif extension from a string. Return values from the commands are provided for clarity. Enter the following command:
% string trim "picture.gif " .gif
picture
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