Shell Programming and Scripting

Id,Text,File
"123","This is unix file","Unix"
"121","This is
C file","C"

Id,Text,File
"123","This","Unix"
"121","This","C"

{
  num_fields = csv_parse($0, csv)
  if (NR>1 && num_fields > 1) csv[2]= substr(csv[2],1,4)

  # param 3 (level) of 3 will force quotes around all fields
  # default is to only quote if needed (e.g. when field contains comma or newline)
  print csv_create(csv, num_fields, NR>1?3:0)
}

$ awk -f trim2.awk.txt infile
Id,Text,File
"123","This","Unix"
"121","This","C"

#!/usr/bin/ksh
awk -v lengths=10,4,10 '
BEGIN { FS = ","  ; OFS = ","
        split(lengths,len,FS)
      }
      { n = 0
        while ( ++n <= NF ) $n = substr($n,1,len[n])
        print
      }' File

Id,Text,File
"123","Th
is is unix file","Unix"

Id,Text,File
"123","Th
is is unix

cat file3.txt
"123","This is unix file","Unix"
"121","This is
 C file","C"

awk -F"," 'BEGIN{print "Id"",""Text"",""File";OFS=",";}
NF==3{split($2,a," ");print $1,a[1]"\"",$3}
NF!=3{getline x;t=sprintf("%s%s", $0,x);split(t,a,",");split(a[2],s," ");
print a[1],s[1]"\"",a[3]}' file3.txt

Id,Text,File
"123","This","Unix"
"121","This","C"

Id,Text,File "123","Th is is unix file","Unix"