How do I add a line break after every 5 fifth semicolon (;) in a text file

Question

The file looks like this (one big line):

a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a; etc......

Now I want to cut the text and do a line break after every fifth semicolon (;) so it looks like this:

a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
etc....

How do I do this?

Answer 1

With tr and paste

tr ';' '\n' < semicolons | paste -d';' - - - - -

Tests

$ cat semicolons
a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a

$ tr ';' '\n' < semicolons | paste -d';'  - - - - -
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a
a;a;a;a;a

Both tr and paste are specified in POSIX standard.

To add the required semicolon ; at the end of the lines

tr ';' '\n' < semicolons | paste -d';' - - - - - | sed s/$/\;/

Tests

$ tr ';' '\n' < semicolons | paste -d';' - - - - - | sed s/$/\;/
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;    

Answer 2

Purely using GNU sed substitution:

sed 's/\(\([^;]*;\)\{5\}\)/\1\n/g'

or without all the escaping backslashes using -E (thanks @JoL):

sed -E 's/(([^;]*;){5})/\1\n/g'

Example:

$ cat test.txt
a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a;a; etc......

$ cat test.txt | sed 's/\(\([^;]*;\)\{5\}\)/\1\n/g'
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a;a;
a;a;a;a; etc......

Explanation:

• \([^;]*;\): regex capture group matching all characters up to and including a semi-colon.
• \(\([^;]*;\)\{5\}\): regex capture group matching five occurrences of the above. In the sed command, this will be matched into \1.
• s/\(\([^;]*;\)\{5\}\)/\1\n/g: substitute (s/) every occurrence (/g) of the group of five occurrences of all characters up to and including a semicolon (\(\([^;]*;\)\{5\}\)) with itself (\1), but followed by a newline character (\n).

Answer 3

Sed editor method we place a newline after the 5th semicolon, print upto the newline, remove upto newline, rinse n repeat till you run out of the pattern space.

$ sed -e 's/;/;\n/5;P;D' file 

With Perl, use semicolon as field separator and print in bunches of 5 with semicolons as OFS and an empty field at the end to get the trailing semicolon printed :

$ perl -F\; -lane '$,=";";
     print splice(@F, 0, 5), q() while @F;
' file 

Using Awk we look at a bunch of 5 fields and append a semicolon to the first 4 and semicolon + newline to the fifth. Then print the fields with a null separating them:

$ awk -F\; -vOFS= '{
        for(i=1; i<=NF; i++)
            $(i) = $(i) (i%5 ? FS : FS RS)
  }1' file

Answer 4

I find that while regexes are appropriate for this kind of task, I always do it with text editor macros for the visual help and simplicity.

Using vim, you can

set textwidth=20

or similarly low and

set wrap

and if the file really needs editing, a simple macro like

qqf;f;f;f;f;i\n99999@q

would do it.