Numbering paragraphs with the 'cat' command

Question

I'm currently trying to find a way to use the cat command to show a text file as automatically numbered paragraphs for a project I'm doing, but I haven't been able to find a single command.

Example:

Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786) was King of Prussia from 1740 until 1786.[1] His most significant accomplishments during his reign included his military victories, his reorganization of Prussian armies, his patronage of the Arts and the Enlightenment in Prussia, and his final success against great odds in the Seven Years' War. 

Frederick was the last titled King in Prussia and declared himself King of Prussia after achieving full sovereignty for all historical Prussian lands. Prussia had greatly increased its territories and became a leading military power in Europe under his rule. He became known as Frederick the Great (Friedrich der Große) and was affectionately nicknamed Der Alte Fritz ("Old Fritz") by the Prussian people.

Then once the command has been input:

1. Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786) was King of Prussia from 1740 until 1786.[1] His most significant accomplishments during his reign included his military victories, his reorganization of Prussian armies, his patronage of the Arts and the Enlightenment in Prussia, and his final success against great odds in the Seven Years' War. 

2.Frederick was the last titled King in Prussia and declared himself King of Prussia after achieving full sovereignty for all historical Prussian lands. Prussia had greatly increased its territories and became a leading military power in Europe under his rule. He became known as Frederick the Great (Friedrich der Große) and was affectionately nicknamed Der Alte Fritz ("Old Fritz") by the Prussian people.

This is something that I honestly thought I'd find easily, but I have not been able to find a single website with an answer on how to do it. (Keep in mind it has to be a variation of the cat command.)

Solution 1

If the paragraph is actually a line like your example, and you have to use only cat, then surely you want -b (number non-empty lines)?

cat -b file

looks like:

     1  Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786) was King of Prussia from 1740 until 1786.[1] His most significant accomplishments during his reign included his military victories, his reorganization of Prussian armies, his patronage of the Arts and the Enlightenment in Prussia, and his final success against great odds in the Seven Years' War. 

     2  Frederick was the last titled King in Prussia and declared himself King of Prussia after achieving full sovereignty for all historical Prussian lands. Prussia had greatly increased its territories and became a leading military power in Europe under his rule. He became known as Frederick the Great (Friedrich der Große) and was affectionately nicknamed Der Alte Fritz ("Old Fritz") by the Prussian people.

To save this in a file instead of printing in the terminal:

cat -b file > file2

_{In case you really need them, you could add the dots after your numbers, though not, afaik, without resorting to using another command to help cat, like sed, which here replaces whitespace and numbers in lines that start with them (since cat -b indents) with the same pattern plus a . to make 1. 2. etc (this was suggested by @terdon so blazingly fast I didn't have time to make it myself & take the credit)}

cat -b file | sed -r 's/^\s+[0-9]+/&./' > file2

Solution 2

In your example, each paragraph is actually just a single line. The only way it would be formed into a paragraph would be by text wrapping in whichever application was being used to display it.

You can number all non-empty lines in a file, using cat with:

cat -b file

If you want to send this to another file, use redirection:

cat -b file > newfile

The man command is really useful for learning about the uses for other commands, for instance man cat gives:

NAME

       cat - concatenate files and print on the standard output

SYNOPSIS

       cat [OPTION]... [FILE]...

DESCRIPTION

       Concatenate FILE(s), or standard input, to standard output.

       -A, --show-all
              equivalent to -vET

       -b, --number-nonblank
              number nonempty output lines, overrides -n

       -e     equivalent to -vE

       -E, --show-ends
              display $ at end of each line

       -n, --number
              number all output lines

       -s, --squeeze-blank
              suppress repeated empty output lines

       -t     equivalent to -vT

       -T, --show-tabs
              display TAB characters as ^I

       -u     (ignored)

       -v, --show-nonprinting
              use ^ and M- notation, except for LFD and TAB

       --help display this help and exit

       --version
              output version information and exit

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

EXAMPLES

       cat f - g
              Output f's contents, then standard input, then g's contents.

       cat    Copy standard input to standard output.

AUTHOR

       Written by Torbjorn Granlund and Richard M. Stallman.

REPORTING BUGS

       Report cat bugs to [email protected]
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report cat translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright  ©  2013  Free Software Foundation, Inc.  License GPLv3+: GNU
       GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free  to  change  and  redistribute  it.
       There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       tac(1)

       The  full  documentation for cat is maintained as a Texinfo manual.  If
       the info and cat programs are properly  installed  at  your  site,  the
       command

              info coreutils 'cat invocation'

       should give you access to the complete manual.

Solution 3

If by "paragraphs" you mean blocks of lines separated by empty lines, you could add the numbering with simple awk command:

awk -v RS= '{print ++i, $0}' file

To preserve the blank lines in the output, you can set the ORS variable to \n\n like this:

awk -v RS= -vORS='\n\n' '{print ++i, $0}' file

If you want to save the output to a new file you can use a redirect like this:

awk -v RS= '{print ++i, $0}' file > newfile

Solution 4

The "paragraphs" are not paragraphs yet, just long lines (as others have noted)

We need to number the lines and then make them into paragraphs You can use fold for this.

cat -b file | fold -sw 80

This numbers non-empty lines, pipes it into fold which keeps the width at 80 characters (or columns) and breaks the line on spaces.

Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786) was King of Prussia from 1740 until 1786.[1] His most significant accomplishments during his reign included his military victories, his reorganization of Prussian armies, his patronage of the Arts and the Enlightenment in Prussia, and his final success against great odds in the Seven Years' War.

Frederick was the last titled King in Prussia and declared himself King of Prussia after achieving full sovereignty for all historical Prussian lands. Prussia had greatly increased its territories and became a leading military power in Europe under his rule. He became known as Frederick the Great (Friedrich der Große) and was affectionately nicknamed Der Alte Fritz ("Old Fritz") by the Prussian people.

     1  Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786)
was King of Prussia from 1740 until 1786.[1] His most significant
accomplishments during his reign included his military victories, his
reorganization of Prussian armies, his patronage of the Arts and the
Enlightenment in Prussia, and his final success against great odds in the Seven
Years' War.

     2  Frederick was the last titled King in Prussia and declared himself King
of Prussia after achieving full sovereignty for all historical Prussian lands.
Prussia had greatly increased its territories and became a leading military
power in Europe under his rule. He became known as Frederick the Great
(Friedrich der Große) and was affectionately nicknamed Der Alte Fritz ("Old
Fritz") by the Prussian people.

---

cat

   -b, --number-nonblank
          number nonempty output lines, overrides -n

fold

   -s, --spaces
          break at spaces

   -w, --width=WIDTH
          use WIDTH columns instead of 80

View more solutions

Comments

[Zanna]

please can you show us an example of what you mean?

[Byte Commander]

So you want to add line numbers to a plain text file?

[Campers]

It would be something similar to that, but I wouldn't want to number EVERY SINGLE line, it'd just be the paragraph, and yes, it is a plain text file

[Byte Commander]

As Zanna said, please give us a short example of maybe two little paragraphs and what output you would like for that.

[Byte Commander]

And would you like unnumbered lines to be indented so that they start in the same column as numbered lines?

[steeldriver]

... in particular, what feature of the text delineates paragraphs (we can guess it might be one or more blank lines, but you need to be specific about that)

[Arronical]

@ByteCommander are you sure you mean -A, seems to just show line-end, tabs and non-printing characters?

[Byte Commander]

@Arronical Oh, no. Good catch, I meant of course -n.

[Byte Commander]

In your example, each "paragraph" is just a single line though. And if you only may use the cat command (smells like homework, btw), you must use cat -n filename. Or cat -b filename as suggested by Zanna and Arronical in their answers.

[Byte Commander]

This does not indent unnumbered lines and it removes blank lines from the output.

[Arronical]

It'd be useful to show the OP the redirection to send this output to another file too.

[user000001]

@ByteCommander: The OP doesn't mention anything about indenting unnumbered lines

[Arronical]

Ooh you're speedy! Does smell like homework though!

[Zanna]

@Arronical shrug sure, but I'm not a detective, I just answer the question ;)

[Byte Commander]

Yes, he doesn't. And looking at the example he just provided, probably he simply wants cat -n, as all his "paragraphs" are just long lines...

[Arronical]

+1 as the OP wasn't totally clear about definitely needing cat in the orignal version of the question.

[Sergiy Kolodyazhnyy]

There's also -n flag i think. Check man page, there's gotta be some difference

[Zanna]

-n is all lines whether empty or not @Serg

[Sergiy Kolodyazhnyy]

@Zanna Ah , so there is a difference !