uniq

Documentation

Overview

Package uniq implements the uniq builtin command.

uniq — report or omit repeated lines

Usage: uniq [OPTION]... [INPUT_FILE]

Filter adjacent matching lines from INPUT_FILE (or standard input), writing to standard output.

With no INPUT_FILE, or when INPUT_FILE is -, read standard input.

Note: the output file argument (second positional arg) supported by GNU uniq is intentionally NOT implemented because it writes to the filesystem, violating the shell's safety rules.

Accepted flags:

-c, --count
    Prefix lines by the number of occurrences.

-d, --repeated
    Only print duplicate lines, one for each group.

-D, --all-repeated[=METHOD]
    Print all duplicate lines. METHOD={none,prepend,separate}
    (default: none). Mutually exclusive with --group.

-u, --unique
    Only print unique lines (lines that are not repeated).

-i, --ignore-case
    Ignore differences in case when comparing lines.

-f N, --skip-fields=N
    Avoid comparing the first N fields. Fields are sequences of
    non-blank characters separated by blanks (spaces and tabs).

-s N, --skip-chars=N
    Avoid comparing the first N characters (applied after field
    skipping).

-w N, --check-chars=N
    Compare no more than N characters in each line.

-z, --zero-terminated
    Line delimiter is NUL (\0), not newline.

--group[=METHOD]
    Show all input lines, separating groups with an empty line.
    METHOD={separate,prepend,append,both} (default: separate).
    Mutually exclusive with -c, -d, -D, -u.

-h, --help
    Print this usage message to stdout and exit 0.

Exit codes:

0  Success.
1  An error occurred (invalid argument, missing file, incompatible flags).

Memory safety:

Lines are processed one at a time via a streaming scanner with a
per-line cap of MaxLineBytes (1 MiB). Only the current and previous
lines are kept in memory. All loops check ctx.Err() to honour the
shell's execution timeout.

Index

• Constants
• Variables

Constants

const MaxCount = 1<<31 - 1 // 2 147 483 647

MaxCount is the maximum accepted value for -f, -s, -w flags.

const MaxLineBytes = 1 << 20 // 1 MiB

MaxLineBytes is the per-line buffer cap for the line scanner.

Variables

var Cmd = builtins.Command{
	Name:        "uniq",
	Description: "report or omit repeated lines",
	MakeFlags:   registerFlags,
}

Cmd is the uniq builtin command descriptor.