Programming

Hi, I have two files:
Input_file1.txt

Code:

124
235
152
178
156
142
178
163
159

Input_file2.txt

Code:

124|5623
452|6698
178|9995
235|7542
159|8852
152|9963
156|8512
885|9956
754|6523

Desired_output.txt:

Code:

124|5623
235|7542
152|9963
178|9995
156|8512
142|
178|9995
163|
159|8852

Rules to follow when writing program:
[code]
1. The sequence of output file Should be in accordance to File 1. If any Value of File 1 is not found in File 2 then second field of Output file should be a blank.
2. Desired format in c program:

Code:

./c_program_name Input_file1.txt Input_file2.txt Desired_output.txt

Awk code that I have tried:

Code:

awk -F"|" ' NR == FNR { arr[$1]=$2; next } {  print $1"|"arr[$1] } '  Input_file2.txt Input_file1.txt > Desired_output.txt

The above awk code work fine for small data.
Unfortunately, it takes a long time for data more than 1Gb
Thanks for any advice.

The first thing I'd do is sort the files, otherwise you have to scan the whole file2 for each line of file1. So you'd either do UNIX sort(1) and use that as input to your program, or you'd implement some sorting within the program.
Once sorted, you just have to search file2 until you hit a line that is greater than the current number from file1 to find out whether file2 contains that number or not.