Math & Sequences

Math & Sequences

seq for generating numeric sequences and expr for arithmetic and string expression evaluation.

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seq

Generate a sequence of numbers, one per line or joined with a separator.

seq [OPTIONS] LAST
seq [OPTIONS] FIRST LAST
seq [OPTIONS] FIRST INCREMENT LAST

Flags

Flag	Description
-s SEP, --separator=SEP	Use SEP as the separator between numbers (outputs a single BashText string instead of individual objects)
-w, --equal-width	Pad numbers with leading zeros so all have equal width

SeqOutput Properties

Without -s, each result is a PsBash.SeqOutput object:

Property	Type	Description
Value	long or double	The numeric value of the sequence element
Index	int	Zero-based position in the sequence
BashText	string	Formatted string representation (includes padding when -w is used)

Note

When -s is used, seq returns a single BashText object with all values joined by the separator instead of individual SeqOutput objects.

Examples

Count from 1 to 5:

seq 5

1
2
3
4
5

Each line is a typed SeqOutput object:

$nums = seq 5
$nums[2].Value   # 3
$nums[2].Index   # 2

Specify a start and end:

seq 3 7

3
4
5
6
7

Custom increment:

seq 0 2 10

0
2
4
6
8
10

Countdown with negative increment:

seq 5 -1 1

5
4
3
2
1

Comma-separated output:

seq -s ', ' 1 5

1, 2, 3, 4, 5

Equal-width zero padding:

seq -w 1 100

001
002
003
...
099
100

Decimal sequences:

seq 0.0 0.5 2.0

0.0
0.5
1.0
1.5
2.0

Pipeline composition — types survive through the pipeline:

seq 1 10 | grep '[13579]$'

1
3
5
7
9

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expr

Evaluate arithmetic, comparison, or string expressions and return the result.

expr EXPRESSION

Expressions use infix notation for arithmetic and comparisons, and keyword-prefix notation for string operations.

Arithmetic Operators

Operator	Description
+	Addition
-	Subtraction
*	Multiplication
/	Integer division (truncates toward zero)
%	Modulus (remainder)

Comparison Operators

Operator	Description
=	Equal (case-sensitive for strings)
!=	Not equal
<	Less than
<=	Less than or equal
>	Greater than
>=	Greater than or equal

Comparisons return 1 for true and 0 for false. When both operands are integers, numeric comparison is used; otherwise string comparison applies.

String Operations

Syntax	Description
expr length STRING	Length of the string
expr substr STRING POS LEN	Substring starting at 1-based POS for LEN characters
expr index STRING CHARS	1-based position of the first character in CHARS found in STRING, or 0 if none
expr match STRING REGEX	Match STRING against a POSIX BRE anchored at start; returns the captured group if \(...\) is present, otherwise the match length

ExprOutput Properties

Each result is a PsBash.ExprOutput object:

Property	Type	Description
Value	long or string	The result as a number (when the result is numeric) or string
BashText	string	String representation of the result

Examples

Basic arithmetic:

expr 2 + 3

5

The result is a typed object:

$r = expr 10 '*' 5
$r.Value   # 50

Tip

Wrap * in quotes to prevent PowerShell from expanding it as a glob. The same applies to < and > which PowerShell interprets as redirection operators.

Integer division and modulus:

expr 17 / 5

3

expr 17 '%' 5

2

Comparison:

expr 10 '>' 5

1

expr 3 '=' 3

1

String length:

expr length 'hello world'

11

Substring extraction:

expr substr 'hello world' 7 5

world

Character index:

expr index 'hello' 'lo'

3

Returns the 1-based position of the first occurrence of any character from the search string. Here l appears at position 3.

Regex match with capture group:

expr match 'archive-2024.tar.gz' '.*-\([0-9]*\)'

2024

The \(...\) capture group extracts the year. Without a capture group, match returns the length of the matched portion.

Single operand passthrough:

expr 'hello'

hello

When given a single operand, expr echoes it as the result.

seq vs expr

	seq	expr
Purpose	Generate number sequences	Evaluate expressions
Output type	SeqOutput per number	Single ExprOutput
Decimal support	Yes	Integer arithmetic only
String operations	No	length, substr, index, match
Pipeline use	Generates multiple objects for piping	Returns a single result