bash - grep-ing a variable vs. a file - execution time -

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made interesting observation - storing output of curl statement in text file , grep-ing strings. later changed code store output variable instead. turns out, change caused script run slower. counter intuitive me since thought i/o operations more expensive in-memory operations. here code:

#!/bin/bash url="http://m.cnbc.com" while read line;   ua=$line   curl -s --location --user-agent "$ua" $url > raw.txt   #raw=`curl --location --user-agent "$ua" $url`   l=`grep -c -e "advertise us" raw.txt`   #l=`echo $raw | grep -c -e "advertise us"`   m=`grep -c -e "id='menu'><button>menu</button>" raw.txt`   #m=`echo $raw | grep -c -e "id='menu'><button>menu</button>"`   d=`grep -c -e "careers" raw.txt`   #d=`echo $raw | grep -c -e "careers"`   if [[ ( $l == 1 && $m == 0 ) && ( $d == 0) ]]           ac="legacy"   elif [[ ( $l == 0 && $m == 1 ) && ( $d == 0) ]]       ac="modern"   elif [[ ( $l == 0 && $m == 0 ) && ( $d == 1) ]]           ac="desktop"   else   ac="unable determine"   fi   echo $ac >> results.txt done < useragents.txt

the commented lines represent storing-in-variable approach. ideas why happening? there ways further speed-up script? right takes 8 minutes process 2000 input entries.

chepner correct. read each call curl once, flagging each of 3 desired strings. here's example code using awk. untested:

url="http://m.cnbc.com" while ifs= read -r line;     raw=$(curl --location --user-agent "$line" $url)      awk '     /advertise us/ {         l=1     }     /id='\''menu'\''><button>menu<\/button>/ {         m=1     }     /careers/ {         d=1     }      end {         if (l==1 && m==0 && d==0) {             s = "legacy"         }         else if (l==0 && m==1 && d==0) {             s = "modern"         }         else if (l==0 && m==0 && d==1) {             s = "desktop"         }         else {             s = "unable determine"         }          print s >> "results.txt"     }' "$raw"  done < useragents.txt

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