17.14: String Formatting
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Overview
String formatting uses a process of string interpolation (variable substitution) to evaluate a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values. [1]
Discussion
Most current programming languages provide one or more string formatting functions that use a template string with placeholders and optional alignment, width, and precision indicators to generate formatted output.
| Language | Function | Examples |
|---|---|---|
| C++ |
snprintf()
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snprintf(str, sizeof(str), "Hello %s!", name);
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| C# |
Format()
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String.Format("Hello {0}!", name);
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| Java |
format()
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String.format("Hello %s!", name);
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| JavaScript | template literal |
`Hello ${name}`;
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| Python |
format()
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"Hello {}!".format(name)
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| Swift |
interpolation
String()
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"Hello \(name)!"
String(format:"%.2f", value)
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String interpolation, like string concatenation, may lead to security problems. If user input data is improperly escaped or filtered, the system may be exposed to code injection. [2]
Key Terms
- code injection
- The exploitation of a computer bug that is caused by processing invalid data. [3]
- formatting
- Modifying the way the output is displayed.
- string interpolation
- Evaluating a string literal containing one or more placeholders, yielding a result in which the placeholders are replaced with their corresponding values.