Finding columns with only white space in a text file and replace them with a unique separator - regex

Question

I have a file like this:
aaa b b ccc 345
ddd fgt f u 3456
e r der der 5 674
As you can see the only way that we can separate the columns is by finding columns that have only one or more spaces. How can we identify these columns and replace them with a unique separator like ,.
aaa,b b,ccc,345
ddd,fgt,f u,3456
e r,der,der,5 674
Note:
If we find all continuous columns with one or more white spaces (nothing else) and replace them with , (all the column) the problem will be solved.
Better explanation of the question by josifoski :
Per block of matrix characters, if all are 'space' then all block should be replaced vertically with one , on every line.

Answer 1

$ cat tst.awk
BEGIN{ FS=OFS=""; ARGV[ARGC]=ARGV[ARGC-1]; ARGC++ }
NR==FNR {
for (i=1;i<=NF;i++) {
if ($i == " ") {
space[i]
}
else {
nonSpace[i]
}
}
next
}
FNR==1 {
for (i in nonSpace) {
delete space[i]
}
}
{
for (i in space) {
$i = ","
}
gsub(/,+/,",")
print
}
$ awk -f tst.awk file
aaa,b b,ccc,345
ddd,fgt,f u,3456
e r,der,der,5 674

Answer 2

Another in awk
awk 'BEGIN{OFS=FS=""} # Sets field separator to nothing so each character is a field
FNR==NR{for(i=1;i<=NF;i++)a[i]+=$i!=" ";next} #Increments array with key as character
#position based on whether a space is in that position.
#Skips all further commands for first file.
{ # In second file(same file but second time)
for(i=1;i<=NF;i++) #Loops through fields
if(!a[i]){ #If field is set
$i="," #Change field to ","
x=i #Set x to field number
while(!a[++x]){ # Whilst incrementing x and it is not set
$x="" # Change field to nothing
i=x # Set i to x so it doesnt do those fields again
}
}
}1' test{,} #PRint and use the same file twice

Answer 3

Since you have also tagged this r, here is a possible solution using the R package readr. It looks like you want to read a fix width file and convert it to a comma-seperated file. You can use read_fwf to read the fix width file and write_csv to write the comma-seperated file.
# required package
require(readr)
# read data
df <- read_fwf(path_to_input, fwf_empty(path_to_input))
# write data
write_csv(df, path = path_to_output, col_names = FALSE)