EXPR(1)

💅 EXPR(1) — the perl-adjacent one, bestie

okay so real talk — this is the User Contributed Perl Documentation page for expr, and it's like, the little math-and-string gremlin that lives in your shell. let's get into it 🎀

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✨ NAME ✨

expr — evaluate expression. that's it. that's the whole gig. she evaluates expressions 💅

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🦋 SYNOPSIS 🦋

expr expression

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🌸 DESCRIPTION 🌸

okay so the expr utility takes expression, evaluates it, and writes the result on standard output. main character energy, honestly ✨

the important vibe check: all operators are separate arguments to the expr utility. like, separate. individual. don't mush them together. and characters that are special to the command interpreter must be escaped — no cap, your shell will absolutely eat them otherwise 😭

operators are listed below in order of increasing precedence. operators with equal precedence are grouped within { } symbols. iykyk 🫶

• expr1 | expr2 — returns the evaluation of expr1 if it's neither an empty string nor zero; otherwise, returns the evaluation of expr2. basically "you first, unless you're nothing" 💖
• expr1 & expr2 — returns the evaluation of expr1 if neither expression evaluates to an empty string or zero; otherwise, returns zero. both gotta show up and both gotta be nonzero, or it's a zero, periodt.
• expr1 {=, >, >=, <, <=, !=} expr2 — returns the results of integer comparison if both arguments are integers; otherwise, returns the results of string comparison using the locale-specific collation sequence. the result of each comparison is 1 if the specified relation is true, or 0 if the relation is false. so like, true or false, binary, iconic 🌈
• expr1 {+, -} expr2 — returns the results of addition or subtraction of integer-valued arguments. math! we love her 🧚
• expr1 {*, /, %} expr2 — returns the results of multiplication, integer division, or remainder of integer-valued arguments. note the integer part, bestie, this is not the place for your decimals 🙈
• expr1 : expr2 — the : operator matches expr1 against expr2, which must be a regular expression. the regular expression is anchored to the beginning of the string with an implicit ^ — so it's matching from the start whether you asked or not, lowkey possessive 💀

the regular expression language is perlre(1). yes, that's the whole perl regex situation, go off 👑

if the match succeeds and the pattern contains at least one regular expression subexpression (...), the string corresponding to $1 is returned; otherwise the matching operator returns the number of characters matched. if the match fails and the pattern contains a regular expression subexpression the null string is returned; otherwise 0.

parentheses are used for grouping in the usual manner. classic.

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💖 EXAMPLES 💖

1. the following example adds one to the variable a. truly the "just one more" of shell scripting ✨

a=`expr $a + 1`

1. the following example returns the filename portion of a pathname stored in variable a. the // characters act to eliminate ambiguity with the division operator — yes she's being careful, we stan a cautious queen 🎀

expr //$a : '.*/\(.*\)'

1. the following example returns the number of characters in variable a. length check, but make it unix 💅

expr $a : '.*'

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🩺 DIAGNOSTICS 🩺

the expr utility exits with one of the following values. exit code check, bestie, always:

• 0 — the expression is neither an empty string nor 0.
• 1 — the expression is an empty string or 0.
• 2 — the expression is invalid. 😭 (this one's the bad one, fr fr)

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📜 STANDARDS 📜

the expr utility conforms to IEEE Std1003.2 (``POSIX.2''). certified. licensed. standardised. we love a compliant icon 👑

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🫶 AUTHOR 🫶

the original Perl implementation was written by Michael Robinson, smrf@sans.vuw.ac.nz. the current version was written by Michael Mikonos and is based on the C version by John T. Conklin. shoutout to the whole lineage, fr fr 💜

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⭐ COPYRIGHT and LICENSE ⭐

this program may be used under the terms of the Artistic License 2.0. read it, respect it, live it 🌸

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reminder: escape your shell-special characters before handing them to expr, or chaos. that's the whole warning. go forth and evaluate, bestie 💅✨

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and that's the page!! brought to you by perl v5.42.2, dated 2026-02-15 — mwah, see you in the next manpage 🎀💖🦋