Shell Programming and Scripting

aaa eee
bbb fff
ccc ggg
ddd hhh

ccc ggg

function read_file_into_array(file, array     ,status, record, count ) {
   count  = 0;
   while (1) {
      status = getline record < file
      if (status == -1) {
         print "Failed to read file " file;
         exit 1;
      }
      if (status == 0) break;
      array[++count] = record;
   }
   close(file);
   return count
}

   records_count = read_file_into_array("input.txt", File);
   print "Records count=" records_count;
   for (i=1; i<=records_count; i++)
      printf "[%d] %s\n", i, File[i];

Line 1
Line 2
Line 3

Records count=3
[1] Line 1
[2] Line 2
[3] Line 3

function read_file_into_array(file, array     ,status, record, count ) {
   count  = 0;
   while (1) {
      status = getline record < file
      if (status == -1) {
         print "Failed to read file " file;
         exit 1;
      }
      if (status == 0) break;
      array[++count] = record;
   }
   close(file);
   return count
}

head -$line_number $file | tail -1

$ cat rany.awk
function read_file_into_array(file, array     ,status, record, count ) {
   count  = 0;
   while (1) {
      status = getline record < file
      if (status == -1) {
         print "Failed to read file " file;
         exit 1;
      }
      if (status == 0) break;
      array[++count] = record;
   }
   close(file);
   return count
}
BEGIN {
   records_count = read_file_into_array("input.txt", File)
   print "The file contains",records_count,"records.\n"
}
{
   printf "Record #%d [%s]\n\n", $1, File[$1];
}
$ cat input.txt
This is record 1
Line 2
Last line
$ awk -f rany.awk
The file contains 3 records.

2
Record #2 [Line 2]

1
Record #1 [This is record 1]

3
Record #3 [Last line]

^D
$

sed -n "$line_number{p;q;}" input.txt

awk NR==$line_number file

awk '{array[NR]=$0}
END{
  print array[i]
  # more stuff with array[]
}' i=$line_number file