csh: while read

eantoranz · 07-08-2009, 03:34 PM

Is there an equivalent in csh to bash's while read variable list?

Uncle_Theodore · 07-08-2009, 04:17 PM

AFAIK, the answer is no.

eantoranz · 07-08-2009, 04:31 PM

Well, I had to do it with a rather long trick:

say, in bash:

Code:

cat /etc/passwd | while read blah; do
    echo $blah
done

in csh:

Code:

set lines=`cat /etc/passwd`
set i=1
while ( $i <= $#lines )
    echo $lines[$i]
    @ i = $i + 1
end

Or something like that

colucix · 07-08-2009, 04:38 PM

Or something like:

Code:

foreach line ( "`cat /etc/passwd`" )
  echo $line
end

eantoranz · 07-08-2009, 04:43 PM

That's right, but in my case I had two variables to get from every line, so I couldn't use the foreach and had to go with the while instead.

colucix · 07-08-2009, 05:17 PM

In C-shell it's not possible to read multiple variables, but you can do a trick like this:

Code:

foreach line ( "`cat file`" )
   set argv = ( $line )
   set name1 = $1
   set name2 = $2
   echo $name1
   echo $name2
end

or eventually use the cut command to split the line into fields, using a custom field separator as : (colon) to parse /etc/passwd.

colucix · 07-08-2009, 05:48 PM

This should work for /etc/passwd:

Code:

foreach line ( "`cat /etc/passwd`" )
   set line = "$line:gas/ /_/"
   set line = "$line:gas/:/ /"
   set argv = ( $line )
   set name1 = $1
   set name2 = "$5:gas/_/ /"
   echo $name2
end

It uses variable modifiers. It replace any blank space with _ (underscore), then any : with a blank space. Finally it extracts the fields, replacing _ with a blank space in those fields where a blank space can appear (needed only for those fields where a blank space can actually appear, like the fifth field).