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man pages section 1: User Commands

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Updated: Wednesday, February 9, 2022



nl - line numbering filter


/usr/bin/nl [-p] [-b [type]] [-d [delim]] [-f [type]] 
     [-h [type]] [-i [incr]] [-l [num]] [-n [format]] 
     [-s [sep]] [-w [width]] [-v [startnum]] [file]
/usr/xpg4/bin/nl [-p] [-b type] [-d delim] [-f type] 
     [-h type] [-i incr] [-l num] [-n format] [-s sep] 
     [-w width] [-v startnum] [file]


The nl utility reads lines from the named file, or the standard input if no file is named, and reproduces the lines on the standard output. Lines are numbered on the left in accordance with the command options in effect.

nl views the text it reads in terms of logical pages. Line numbering is reset at the start of each logical page. A logical page consists of a header, a body, and a footer section. Empty sections are valid. Different line numbering options are independently available for header, body, and footer. For example, –bt (the default) numbers non-blank lines in the body section and does not number any lines in the header and footer sections.

The start of logical page sections are signaled by input lines containing nothing but the following delimiter character(s):

Line contents
Start Of

Unless optioned otherwise, nl assumes the text being read is in a single logical page body.


Command options may appear in any order and may be intermingled with an optional file name. Only one file may be named. The specified default is used when the option is not entered on the command line. /usr/xpg4/bin/nl options require option arguments. A SPACE character may separate options from option arguments. /usr/bin/nl options may have option arguments. If option-arguments of /usr/bin/nl options are not specified, these options result in the default. The supported options are:


Specifies which logical page body lines are to be numbered. Recognized types and their meanings are:


number all lines


number all non-empty lines.


no line numbering


number only lines that contain the regular expression specified in exp. See NOTES below.

Default type for logical page body is t (text lines numbered).


Same as –btype except for footer. Default type for logical page footer is n (no lines numbered).


The two delimiter characters specifying the start of a logical page section may be changed from the default characters (\ : ) to two user-specified characters. If only one character is entered, the second character remains the default character (:). No space should appear between the –d and the delimiter characters. To enter a backslash, use two backslashes.


Same as –btype except for header. Default type for logical page header is n (no lines numbered).


incr is the increment value used to number logical page lines. Default incr is 1.


num is the number of blank lines to be considered as one. For example, −l2 results in only the second adjacent blank being numbered (if the appropriate –ha, –ba, and/or –fa option is set). Default num is 1.


format is the line numbering format. Recognized values are:


left justified, leading zeroes suppressed


right justified, leading zeroes suppressed


right justified, leading zeroes kept

Default format is rn (right justified).


Do not restart numbering at logical page delimiters.


sep is the character(s) used in separating the line number and the corresponding text line. Default sep is a TAB.


startnum is the initial value used to number logical page lines. Default startnum is 1.


width is the number of characters to be used for the line number. Default width is 6.


The following operand is supported:


A path name of a text file to be line-numbered.


Example 1 An example of the nl command

The command:

example% nl -v10 -i10 -d!+ filename1

will cause the first line of the page body to be numbered 10, the second line of the page body to be numbered 20, the third 30, and so forth. The logical page delimiters are !+.

Environment Variables

See environ(7) for descriptions of the following environment variables that affect the execution of nl: LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:


Successful completion.


An error occurred.



Collation table generated by localedef


Shared object containing string transformation library routines


See attributes(7) for descriptions of the following attributes:




Interface Stability

See Also

pr(1), regex(7), attributes(7), environ(7), regexp(7), standards(7)


Internationalized Regular Expressions are used in the POSIX and "C" locales. In other locales, Internationalized Regular Expressions are used if the following two conditions are met:

  • /usr/lib/locale/locale/LC_COLLATE/CollTable is present.

  • /usr/lib/locale/locale/LC_COLLATE/coll.so is not present.

Otherwise, Simple Regular Expressions are used.

Internationalized Regular Expressions are explained on regex(7). Simple Regular Expressions are explained on regexp(7).