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A page for each applet in the kit, plus .so stubs for aliases such as egrep and unxz. Each was written from the pinned busybox-w32 source with the kit's patches and configuration, then checked against the source and by experiment. The NOTES sections cover Windows behavior. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
300 lines
5.9 KiB
Groff
300 lines
5.9 KiB
Groff
.TH CAT 1 2026-10-19 "w64devkit" "w64devkit Manual"
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.SH NAME
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cat \- concatenate files to standard output
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.SH SYNOPSIS
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.B cat
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.RB [ \-nbvteAu ]
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.RI [ file ...]
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.SH DESCRIPTION
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.B cat
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writes the contents of each
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.I file
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to standard output, in order.
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With no
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.I file
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operands, or for a
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.I file
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named
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.BR \- ,
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it reads standard input.
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A
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.I file
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that cannot be opened is reported on standard error and skipped, and the
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remaining files are still written.
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A read error ends that file.
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It is reported only without options, and with
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.B \-n
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or
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.B \-b
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alone it does not affect the exit status.
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.PP
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Without options, the bytes are copied unchanged.
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The options number the lines, show nonprinting characters, or both.
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.SS Line numbers
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With
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.B \-n
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or
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.BR \-b ,
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a numbered line starts with its number, right-aligned in 6 columns,
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and a tab.
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Numbering starts at 1 and continues across files.
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.PP
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Without
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.BR \-v ,
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.BR \-t ,
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.BR \-e ,
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or
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.BR \-A ,
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the input is read as lines of text, which changes it: a CR before an LF
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is removed, a NUL byte ends a line and is removed, and every line is
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written with a final LF, including the last line of a file that has
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none.
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.PP
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With any of them, the number is followed by two spaces instead of a
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tab, and lines end only at LF: a CR or NUL is shown like any other byte.
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A file that does not end with an LF then runs into the first line of the
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next file, which gets no number.
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.SS Nonprinting characters
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With
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.BR \-v ,
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.BR \-t ,
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.BR \-e ,
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or
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.BR \-A ,
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each byte is written as follows, so the output is plain ASCII:
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.IP \(bu 2
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LF and the printable ASCII characters 0x20 to 0x7E are written as
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themselves, and so is tab, unless
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.B \-t
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is given.
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.IP \(bu 2
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Any other byte below 0x20 is
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.B \(ha
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followed by the character 0x40 above it, from
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.B \(ha@
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to
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.BR \(ha_ ,
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so CR is
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.B \(haM
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and ESC is
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.BR \(ha[ .
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DEL, 0x7F, is
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.BR \(ha? .
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.IP \(bu 2
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A byte from 0x80 to 0xFF is
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.B M\-
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followed by the byte 0x80 below it, written as itself if printable and
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in
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.B \(ha
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form otherwise, so 0x8A is
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.B M\-\(haJ
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and 0xFF is
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.BR M\-\(ha? .
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Text in UTF-8 appears byte by byte: the encoding of
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.B e
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with an acute accent, 0xC3 0xA9, is
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.BR M\-CM\-) .
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.SH OPTIONS
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Options may be grouped, as in
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.BR \-vn ,
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and may follow
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.I file
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operands.
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.B \-\-
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ends the options.
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.TP
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.B \-n
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Number every output line, as described under
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.BR "Line numbers" .
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.TP
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.B \-b
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Number only nonempty lines.
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Empty lines are written without a number and are not counted.
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Without
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.BR \-v ,
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.BR \-t ,
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.BR \-e ,
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or
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.BR \-A ,
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a line holding only a CR is empty.
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Overrides
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.BR \-n .
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.TP
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.B \-v
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Show nonprinting characters, as described under
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.BR "Nonprinting characters" .
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.TP
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.B \-t
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Like
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.BR \-v ,
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and also show each tab as
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.BR \(haI .
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.TP
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.B \-e
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Like
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.BR \-v ,
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and also write
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.B $
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before each LF.
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A last line without an LF gets no
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.BR $ .
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.TP
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.B \-A
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Same as
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.BR \-vte .
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.TP
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.B \-u
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Accepted for compatibility and ignored.
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.TP
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.B \-\-help
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Print a usage message on standard output and exit.
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It is recognized only as the first argument.
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.SH ENVIRONMENT
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.TP
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.B POSIXLY_CORRECT
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When set, the first
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.I file
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operand ends the options, so that later arguments such as
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.B \-n
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are file names.
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.TP
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.B BB_GLOBBING
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Unless it is
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.BR 0 ,
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wildcards in the operands are expanded, as needed when run from
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.BR cmd.exe .
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A busybox process started with it unset sets it to
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.B 0
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for its children, so commands run from the kit's shell receive their
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operands as the shell expanded them.
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.TP
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.BR LC_ALL ", " LC_CTYPE ", " LANG
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If the first of these that is set has the value
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.BR C ,
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output to a console is not converted, as described in
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.BR NOTES ,
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and the console interprets the bytes in its own code page.
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.PP
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Variables that affect every busybox applet, such as
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.B BB_TERMINAL_MODE
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for console output, are described in
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.BR busybox (1).
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.SH EXIT STATUS
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.TP
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.B 0
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Success.
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.TP
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.B 1
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An invalid option, a
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.I file
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could not be opened or read, or standard output could not be written.
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.TP
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.B 141
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Standard output is a pipe that was closed before all output was written.
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.SH EXAMPLES
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Reassemble a file cut into pieces by
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.BR split :
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.PP
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.RS 4
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.EX
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$ cat backup.zip.?? >backup.zip
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.EE
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.RE
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.PP
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Number the lines of a source file:
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.PP
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.RS 4
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.EX
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$ cat \-n main.c
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.EE
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.RE
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.PP
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Reveal CR line endings, tabs, and trailing spaces:
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.PP
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.RS 4
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.EX
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$ printf \(aqone\er\entwo\etthree \en\(aq | cat \-A
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one\(haM$
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two\(haIthree $
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.EE
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.RE
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.PP
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Write a file from a here-document:
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.PP
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.RS 4
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.EX
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$ cat >config.h <<EOF
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> #define VERSION "1.0"
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> EOF
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.EE
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.RE
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.SH NOTES
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Differences from GNU cat:
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.IP \(bu 2
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There are no long options, and no
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.BR \-E ,
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.BR \-T ,
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or
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.BR \-s .
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.IP \(bu 2
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With
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.B \-n
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or
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.B \-b
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alone, line endings change, as described under
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.BR "Line numbers" .
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.IP \(bu 2
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With
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.BR \-v ,
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.BR \-t ,
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.BR \-e ,
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or
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.BR \-A ,
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line numbers are followed by two spaces, not a tab.
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.PP
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Standard input and output are binary, so without options CR LF line
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endings and Ctrl-Z characters are copied unchanged.
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.PP
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File names may use drive letters and backslashes.
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They may contain any Unicode characters on Windows 10 version 1903 and
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later, and are limited to the system code page on earlier versions.
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The device names
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.IR /dev/null ,
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.IR /dev/zero ,
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.IR /dev/urandom ,
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.IR /dev/stdin ,
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.I /dev/tty
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(the console), and
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.I /dev/fd/N
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work as on Unix.
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A directory operand fails with
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.BR "Permission denied" ,
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or with
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.B \-n
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or
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.B \-b
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alone,
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.BR "Is a directory" .
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.PP
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Lines typed at a console arrive with CR LF line endings.
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To end the input, type Ctrl-Z at the start of a line and press Enter.
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Ctrl-D is an ordinary character.
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.PP
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When standard output is a console, text is converted for display from
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the ANSI code page, which is UTF-8 on Windows 10 version 1903 and later.
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Escape sequences, such as those for color, take effect, and busybox
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emulates them on consoles without virtual terminal support.
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Without options, output is written in blocks as it is read, and a block
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that contains a NUL byte is written as is, with no conversion or
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emulation.
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.SH SEE ALSO
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.BR busybox (1),
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.BR dos2unix (1),
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.BR head (1),
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.BR less (1),
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.BR nl (1),
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.BR split (1),
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.BR tac (1),
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.BR tee (1),
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.BR xxd (1)
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