Vertical Line

| (Vertical Line) is ASCII code point 124 (0x7C), Unicode U+007C, and a printable punctuation character. It draws a straight vertical stroke — a clean, upright divider that in prose occasionally separates alternatives in linguistic notation or stands between items in a table, though most people outside programming rarely type it. Code gives the pipe character relentless employment. In Unix shells, it chains commands together: cat file | grep "error" | wc -l sends each program's output into the next program's input, a compositional elegance that defines the Unix philosophy. C-family languages use | for bitwise OR and || for logical OR with short-circuit evaluation. JavaScript and Python recently adopted | for additional duties — JavaScript's pipeline proposal and Python's type union syntax (int | str in type hints) both lean on it. CSS uses it in selectors for attribute matching, and regular expressions treat | as alternation: cat|dog matches either word. The trap is a shell classic: in a pipeline, each command runs in a subshell, so variable assignments inside a piped while read loop vanish when the loop ends. Developers set a variable confidently inside the loop, use it afterward, and find it empty — the pipe created an invisible boundary that swallowed their state. The vertical bar's computing origins trace to Bob Bemer's ASCII work in the 1960s, where it was included partly to support logical OR notation in early programming languages. UTF-8 encodes it as a single byte 0x7C. Unicode classifies it as Sm (Symbol, Math) with the name VERTICAL LINE. The broken bar ¦ (U+00A6) is its fractured sibling — once common on European keyboards and occasionally still aliased to the same physical key, producing mysterious syntax errors when it lands in a shell script instead of the solid pipe the parser expects.