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Output of entire files

These commands read and write entire files, possibly transforming them in some way.

cat: Concatenate and write files

cat copies each file (- means standard input), or standard input if none are given, to standard output. Synopsis:

cat [option] [file]...

The program accepts the following options. Also see section Common options.

-A --show-all -A --show-all Equivalent to -vET.

-b --number-nonblank -b --number-nonblank Number all nonblank output lines, starting with 1.

-e -e Equivalent to -vE.

-E --show-ends -E --show-ends Display a $ after the end of each line.

-n --number -n --number Number all output lines, starting with 1.

-s --squeeze-blank -s --squeeze-blank Replace multiple adjacent blank lines with a single blank line.

-t -t Equivalent to -vT.

-T --show-tabs -T --show-tabs Display TAB characters as ^I.

-u -u Ignored; for Unix compatibility.

-v --show-nonprinting -v --show-nonprinting Display control characters except for LFD and TAB using ^ notation and precede characters that have the high bit set with M-.

tac: Concatenate and write files in reverse

tac copies each file (- means standard input), or standard input if none are given, to standard output, reversing the records (lines by default) in each separately. Synopsis:

tac [option]... [file]...

Records are separated by instances of a string (newline by default). By default, this separator string is attached to the end of the record that it follows in the file.

The program accepts the following options. Also see section Common options.

-b --before -b --before The separator is attached to the beginning of the record that it precedes in the file.

-r --regex -r --regex Treat the separator string as a regular expression.

-s separator --separator=separator -s --separator Use separator as the record separator, instead of newline.

nl: Number lines and write files

nl writes each file (- means standard input), or standard input if none are given, to standard output, with line numbers added to some or all of the lines. Synopsis:

nl [option]... [file]...

nl decomposes its input into (logical) pages; by default, the line number is reset to 1 at the top of each logical page. nl treats all of the input files as a single document; it does not reset line numbers or logical pages between files.

A logical page consists of three sections: header, body, and footer. Any of the sections can be empty. Each can be numbered in a different style from the others.

The beginnings of the sections of logical pages are indicated in the input file by a line containing exactly one of these delimiter strings:

\:\:\: start of header; \:\: start of body; \: start of footer.

The two characters from which these strings are made can be changed from \ and : via options (see below), but the pattern and length of each string cannot be changed.

A section delimiter is replaced by an empty line on output. Any text that comes before the first section delimiter string in the input file is considered to be part of a body section, so nl treats a file that contains no section delimiters as a single body section.

The program accepts the following options. Also see section Common options.

-b style --body-numbering=style -b --body-numbering Select the numbering style for lines in the body section of each logical page. When a line is not numbered, the current line number is not incremented, but the line number separator character is still prepended to the line. The styles are:
a number all lines, t number only nonempty lines (default for body), n do not number lines (default for header and footer), pregexp number only lines that contain a match for regexp.

-d cd --section-delimiter=cd -d --section-delimiter Set the section delimiter characters to cd; default is \:. If only c is given, the second remains :. (Remember to protect \ or other metacharacters from shell expansion with quotes or extra backslashes.)

-f style --footer-numbering=style -f --footer-numbering Analogous to --body-numbering.

-h style --header-numbering=style -h --header-numbering Analogous to --body-numbering.

-i number --page-increment=number -i --page-increment Increment line numbers by number (default 1).

-l number --join-blank-lines=number -l --join-blank-lines Consider number (default 1) consecutive empty lines to be one logical line for numbering, and only number the last one. Where fewer than number consecutive empty lines occur, do not number them. An empty line is one that contains no characters, not even spaces or tabs.

-n format --number-format=format -n --number-format Select the line numbering format (default is rn):

ln ln format for nl left justified, no leading zeros; rn rn format for nl right justified, no leading zeros; rz rz format for nl right justified, leading zeros.

-p --no-renumber -p --no-renumber Do not reset the line number at the start of a logical page.

-s string --number-separator=string -s --number-separator Separate the line number from the text line in the output with string (default is TAB).

-v number --first-page=number -v --first-page Set the initial line number on each logical page to number (default 1).

-w number --number-width=number -w --number-width Use number characters for line numbers (default 6).

od: Write files in octal or other formats

od writes an unambiguous representation of each file (- means standard input), or standard input if none are given. Synopsis:

od [option]... [file]...
od -C [file] [[+]offset [[+]label]]

Each line of output consists of the offset in the input, followed by groups of data from the file. By default, od prints the offset in octal, and each group of file data is two bytes of input printed as a single octal number.

The program accepts the following options. Also see section Common options.

-A radix --address-radix=radix -A --address-radix Select the base in which file offsets are printed. radix can be one of the following:
d decimal; o octal; x hexadecimal; n none (do not print offsets).

The default is octal.

-j bytes --skip-bytes=bytes -j --skip-bytes Skip bytes input bytes before formatting and writing. If bytes begins with 0x or 0X, it is interpreted in hexadecimal; otherwise, if it begins with 0, in octal; otherwise, in decimal. Appending b multiplies bytes by 512, k by 1024, and m by 1048576.

-N bytes --read-bytes=bytes -N --read-bytes Output at most bytes bytes of the input. Prefixes and suffixes on bytes are interpreted as for the -j option.

-s [n] --strings[=n] -s --strings Instead of the normal output, output only string constants: at least n (3 by default) consecutive ASCII graphic characters, followed by a null (zero) byte.

-t type --format=type -t --format Select the format in which to output the file data. type is a string of one or more of the below type indicator characters. If you include more than one type indicator character in a single type string, or use this option more than once, od writes one copy of each output line using each of the data types that you specified, in the order that you specified.

a named character, c ASCII character or backslash escape, d signed decimal, f floating point, o octal, u unsigned decimal, x hexadecimal.

The type a outputs things like sp for space, nl for newline, and nul for a null (zero) byte. Type c outputs , \n, and \0, respectively.

Except for types a and c, you can specify the number of bytes to use in interpreting each number in the given data type by following the type indicator character with a decimal integer. Alternately, you can specify the size of one of the C compiler's built-in data types by following the type indicator character with one of the following characters. For integers (d, o, u, x):

C char, S short, I int, L long.

For floating point (f):

F float, D double, L long double.

-v --output-duplicates -v --output-duplicates Output consecutive lines that are identical. By default, when two or more consecutive output lines would be identical, od outputs only the first line, and puts just an asterisk on the following line to indicate the elision.

-w[n] --width[=n] -w --width Dump n input bytes per output line. This must be a multiple of the least common multiple of the sizes associated with the specified output types. If n is omitted, the default is 32. If this option is not given at all, the default is 16.

The next several options map the old, pre-POSIX format specification options to the corresponding POSIX format specs. GNU od accepts any combination of old- and new-style options. Format specification options accumulate.

-a -a Output as named characters. Equivalent to -ta.

-b -b Output as octal bytes. Equivalent to -toC.

-c -c Output as ASCII characters or backslash escapes. Equivalent to -tc.

-d -d Output as unsigned decimal shorts. Equivalent to -tu2.

-f -f Output as floats. Equivalent to -tfF.

-h -h Output as hexadecimal shorts. Equivalent to -tx2.

-i -i Output as decimal shorts. Equivalent to -td2.

-l -l Output as decimal longs. Equivalent to -td4.

-o -o Output as octal shorts. Equivalent to -to2.

-x -x Output as hexadecimal shorts. Equivalent to -tx2.

-C --traditional --traditional Recognize the pre-POSIX non-option arguments that traditional od accepted. The following syntax:

od --traditional [file] [[+]offset[.][b] [[+]label[.][b]]]

can be used to specify at most one file and optional arguments specifying an offset and a pseudo-start address, label. By default, offset is interpreted as an octal number specifying how many input bytes to skip before formatting and writing. The optional trailing decimal point forces the interpretation of offset as a decimal number. If no decimal is specified and the offset begins with 0x or 0X it is interpreted as a hexadecimal number. If there is a trailing b, the number of bytes skipped will be offset multiplied by 512. The label argument is interpreted just like offset, but it specifies an initial pseudo-address. The pseudo-addresses are displayed in parentheses following any normal address.



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