37

I have simple text file named "example".

Reading with terminal command: cat example

Output:

abc cdef ghi jk lmnopq rst uv wxyz

I want to convert (transform) into following form: (expected output from cat example)

abc
cdef
ghi
jk
lmnopq
rst
uv
wxyz

How can I do this via the command-line?

(This is only an example file, I want to convert word's position in vertical-column)

1

6 Answers 6

73

A few choices:

  1. The classic, use tr:

    tr ' ' '\n' < example
    
  2. Use cut

    cut -d ' ' --output-delimiter=$'\n' -f 1- example
    
  3. Use sed

    sed 's/ /\n/g' example
    
  4. Use perl

    perl -pe 's/ /\n/g' example
    
  5. Use the shell

    foo=$(cat example); echo -e "${foo// /\\n}"
    
7
  • 1
    For the sed example I needed to add a $ to get bash to replace with an actual newline ie: sed $'s/ /\\\n/g' example
    – acumartini
    Sep 9, 2019 at 20:38
  • 1
    Above example for OSX sed, for gnu-sed: sed $'s/ /\\n/g'
    – acumartini
    Sep 9, 2019 at 20:44
  • 2
    @acumartini GNU sed (which is the default on Ubuntu, the others aren't relevant on this site) can deal with \n without requiring ANSI-C quotes. So on a GNU system, sed 's/ /\n/g' example works fine and there is no need for sed $'s/ /\\n/g'. You needed to add the $ because macOS uses BSD sed, but that isn't on topic here.
    – terdon
    Feb 24, 2021 at 10:51
  • the lowest denomitator (from sh) is to represent the new line char as $'\n' - like in the example for cut - applicable to all the rest of the examples as well Dec 11, 2022 at 12:47
  • @RadagasttheBrown not sure what you mean. The $'\n' syntax is the more limited approach since it is the only one that requires a shell that understands $'\n' (for example, dash doesn't work well with it). The rest all use robust, portable solutions. So you would never use $'\n' in the other commands since that would only make them slightly less universal.
    – terdon
    Dec 12, 2022 at 11:55
17

Try the below command:

awk -v RS=" " '{print}' file

Or:

awk -v RS='[\n ]' '{print}' file

Example:

$ awk -v RS=" " '{print}' example
abc
cdef
ghi
jk
lmnopq
rst
uv
wxyz

Explanation:

RS (Record Separator) is a built-in awk variable. In the first command, the value given to the RS variable is space (" "). awk breaks the line from printing whenever it finds a space.

In the second command, the value given to the RS variable is a new line character or space ('[\n ]'). This command eliminates the extra blank line that appears when running the first command.

0
11

You can use xargs,

cat example | xargs -n 1

or, better

xargs -n 1 < example
0
3

Using a perl oneliner:

perl -p -i -e 's/\s/\n/g' example

It will replace spaces and tabs with "ENTER" (aka \n)

0
3

No one posted python, so here's that:

python -c "import sys;lines=['\n'.join(l.strip().split()) for l in sys.stdin.readlines()];print('\n'.join(lines))" < input.txt 

We redirect input file into python's stdin stream, and read it line by line. Each line is stripped of its trailing newline, split into words, and then rejoined into one string where each word is separated by newline.This is done to ensure having one word per line and avoid multiple newlines being inserted in case there's multiple spaces next to each other. Eventually we end up with list of strings, which is then again joined into larger string, and printed out to stdout stream. That later can be redirected to another file with > out.txt redirection.

2

Similar to the tr in @terdon's answer, but with the additions:

  • Also works for tabs

  • Converts multiple spaces or tabs to 1 newline

tr -s '[:space:]' '\n' < example
1
  • This was the fastest for me, processing millions of lines.
    – osolmaz
    Sep 19, 2021 at 19:21

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