Textsubstitution

Text substitution is a general technique in text processing that replaces segments of text with alternative strings according to predefined rules, mappings, or data inputs. It is used in document generation, programming, data processing, and communication to produce customized output, transform data, or remove sensitive information.

Forms of substitution vary by domain. In text editors and word processors, find-and-replace operations substitute a target substring with a replacement. These can be literal or pattern-based, often using regular expressions, and can apply to a single document or across multiple files. In programming and templating, macro expansion or templating engines substitute placeholders with actual values at runtime or during generation, enabling personalized letters, reports, or code generation. Text expansion systems replace short abbreviations with longer phrases to speed up typing.

Substitution also appears in cryptography and data privacy. Substitution ciphers replace each letter with another according to a fixed mapping, as seen in simple puzzles or historical codes. Redaction and anonymization use substitution to conceal information by replacing identifiers with tokens such as [REDACTED] or pseudonyms.

Tools and approaches vary. Common utilities include editors with regex support and scripting languages (such as sed, awk, perl, Python, or JavaScript) for programmatic substitution. Templating and interpolation libraries (Mustache, Jinja, or language-native features) provide structured substitution in generated text. Limitations include context sensitivity, risk of unintended replacements, and performance considerations with large datasets or complex patterns.