so let's say i have
aaa
bbb
ccc
ddd
and i need to replace all new lines by comma and space, and end with a dot like so
aaa, bbb, ccc, ddd.
I found this, but i can't understand it at all and i need to know what every single character does ;
... | awk '{ printf $0", " }' | sed 's/.\{2\}$/./'
Can someone make those two commands human-readable ? tysm!
About the command:
... | awk '{ printf $0", " }' | sed 's/.\{2\}$/./'
Awk prints the line $0 followed by , without newlines. When this is done, you have , trailing at the end.
Then the pipe to sed replaces the last , with a single dot as this part .\{2\}$ matches 2 times any character at the end of the string.
With sed using a single command, you can read all lines using N to pull the next line in the pattern space, and use a label to keep on replacing a newline as long as it is not the last line last line.
After that you can append a dot to the end.
sed ':a;N;$!ba;s/\n/, /g;s/$/./' file
Output
aaa, bbb, ccc, ddd.
ok, first of all; thank u.
I do now understand that printf $0", " means 'print every line, and ", " at the end of each'
as for the sed command, a colleague explained it to me a minute ago;
in 's/.\{2\}$/./',
s/ replace
. any character
{2} x2, so two characters
$ at end of the line
/ by ( 's/ / /' = replace/ this / that /)
. the character '.'
/ end
without forgetting to escape { and }, so u end up with
's/ . \{2\} $ / . /'
but wait, it gets even better;
my colleague also told me that \{2\} wasn't necessary in this case ;
.{2} (without the escapes) could simply be replaced by
.. 'any character' twice.
so 's/..$/./' wich is way more readable i think
'replace/ wich ever two last characters / this character/'
hope this helps if any other 42 student gets here
tism again
awk '{ printf $0", " }'
This is awk command with single action, encased in {...}, this action is applied to every line of input.
Printf is print with format, here no formatting takes places but another feature of printf is leveraged - printf does not attach output row separator (default: newline) as opposed to print.
$0 denotes whole current line (sans trailing newline).
", " is string literal for comma followed by space.
$0", " instructs awk to concatenate current line with comma and space.
Whole command thus might be read as: for every line output current line followed by comma and space
sed 's/.\{2\}$/./'
s is one of commands, namely substitute, basic form is
s/regexp/replacement/
therefore
.\{2\}$ is regular expression, . denotes any characters, \{2\} repeated 2 times, $ denotes end of line, thus this one matches 2 last characters of each line, as text was already converted to single line, it will match 2 last characters of whole text.
. is replacement, literal dot character
Whole command thus might be read as: for every line replace 2 last characters using dot
Assuming the four lines are in a file...
#!/bin/sh
cat << EOF >> ed1
%s/$/,/g
$
s/,/./
wq
EOF
ed -s file < ed1
cat file | tr '\n' ' ' > f2
mv f2 file
rm -v ./ed1
echo 'aaa bbb ccc ddd' | mawk NF+=RS FS='\412' RS= OFS='\40\454' ORS='\456\12'
aaa, bbb, ccc, ddd.
