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hello i was trying to read a line to array using ksh script . But some of its values are stored multiple times in adjacent array elements when there is a comma in the field value. How can this is avoided my delimiter is ~

input

17~4~~~char~Y~\"[_a-zA-Z0-9\.]\+@[a-zA-Z0-9]\+\.[a-z]\{2,\}\"~40~email id

code

while IFS= read -r line
  do
   
        if [ $n != 1 ]; then
                IFS="~"
  
                set -A star $line
                col_pos=${star[1]}
                col_patt=${star[6]}
                col_len=${star[7]}
                col_file_id=${star[0]}

value of $line

 17 4   char Y \"[_a-zA-Z0-9\.]\+@[a-zA-Z0-9]\+\.[a-z]\2\" \"[_a-zA-Z0-9\.]\+@[a-zA-Z0-9]\+\.[a-z]\\\" 40 email id

The issue is that pattern ("[_a-zA-Z0-9.]+@[a-zA-Z0-9]+.[a-z]\2") is duplicated while reading, but in actual input file the pattern field is defined once.

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2 Answers 2

Reset to default
1

In:

set -A star $line

as $line is unquoted, you're invoking the split+glob operator. Here, you do want the split part, but not the glob part, so you should disable it first with:

set -o noglob

As @Isaac correctly identified, your issue here is not so much with globbing but with brace expansion that is done by ksh (and only ksh¹) in addition to globbing but is also disabled when globbing is disabled.

set -A array x y z was the ksh88 / pdksh way to set arrays as a whole. Newer versions of ksh including ksh93 and mksh have adopted the zsh-style array=(x y z).

With the set -A syntax, you need:

set -A array -- values

(except in zsh when not emulating ksh), as otherwise, it would not work properly if the first value started with - or +.

So:

set -o noglob; IFS='~'
while IFS= read -r line
do
  if [ "$n" != 1 ]; then
    set -A star -- $line
    col_pos=${star[1]}
    col_patt=${star[6]}
    col_len=${star[7]}
    col_file_id=${star[0]}

Though here, I would avoid all those problems and use this standard sh syntax:

while IFS='~' read -r col_file_id col_pos x x x x col_patt col_len x
do
  if [ "$n" != 1 ]; then

¹ unless POSIX mode is enabled in mksh and some recent versions of ksh93 or when brace expansion is disabled altogether at compile time

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Issues:

  1. The script is incomplete (Missing done, missing fi, etc.).
  2. Variables should be quoted (always, by default).

But your main problem lies in the brace expression {2,} which will repeat the string before and end it in 2 and nothing when expanded in set -A star $line.

An unquoted $line will be subject to several expansions, one of them is brace expansion {,}.

To split the string, without expanding it unquoted, using ~ as delimiter and place the values in an array, this might work:

while IFS= read -r onestar; do star+=("$onestar"); done <<<"${line//~/$'\n'}"

Provided line is one line (contains no newlines), which it should, should it not?

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2
  • i tried like set -A star "$line" but it is not splitting based on "~" star{0} is giving me value '17~1~~~char~Y~[0-9]+~10~number' Commented Jun 9, 2021 at 20:18
  • 1
    Splitting strings based on a delimiter is a quite difficult issue in shell (to be done right). I have edited a correct solution in my answer. @daturmgirl Commented Jun 9, 2021 at 20:30

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