'Can I use awk in a conditional statement

I need to be able to search a user file and determine whether an input from a user is in that file. This does not work

if [ $uname == awk '{print $1}' user_file ]; then echo "success";  fi

basically I am looking for a way to return true if the name is in my user_file. Any examples I find of using if/then deal with integers for comparison. Can you not compare strings in bash?

user_file contains

username1 password
username2 password2

I am trying to write a script that checks that user_info file and if the user has entered the correct username and password then it will perform some other action.

if [ username/password in user_info ]; then [ do some other action ]

(yes, this is an assignment for a class. The instructor isn't great so I'm stuck googling and trying to figure out a lot of things on my own. So I'm not trying to get exact answers to my scripting question, I just need to figure out how if/then loops work with strings.)

bashif-statementawk


Solution 1:[1]

if awk -v uname="$uname" '$1==uname{f=1; exit} END{exit !f}' user_file; then echo "success"; fi

Solution 2:[2]

  • uname is "${u1}" here, and
  • pword is "${p1}"

I intentionally put the only copy of it in the 2nd to last row to make sure it has to scan through the whole file -

unless you're talking about 9 GB or larger file, I think one can save more time to scan it once it's all loaded instead of row by row and doing it piecemeal - 1.35GB input confirmed either found or not within 1.2 secs :::

    % f='test_userpass2.txt' ;
      ( time ( pvE0 <  "${f}" \
         \
         | mawk2 '
           END { exit +RS^index($+RS,__)   # this version won't match
                                           # because i hyphenated them
                  
           }' RS='^$' __="${u1}-${p1}" FS='^$' \
      )
      echo "\n\n exit code : ${?}\n" ) | ecp            
      sleep 3; 
      ( time ( pvE0 < "${f}" \ 
        \
         | mawk2 '
           END { exit +RS^index($+RS,__) 
                  
            }' RS='^$' __="${u1} ${p1}" FS='^$' ) ;
      
       echo "\n\n exit code : ${?}\n" ) | ecp; 

 
      in0: 1.35GiB 0:00:00 [3.46GiB/s] [3.46GiB/s][========>] 100% 

     ( pvE 0.1 in0 < "${f}" | mawk2 'END { exit +RS^index($+RS,__) }' RS='^$'  ; )

    0.54s user 0.64s system 101% cpu 1.160 total


 exit code : 1

 
 
      in0: 1.35GiB 0:00:00 [3.43GiB/s] [3.43GiB/s][=========>] 100% 
       
     ( pvE 0.1 in0 < "${f}" | mawk2 'END { exit +RS^index($+RS,__) }' RS='^$'  ; )  

 0.56s user 0.61s system 98% cpu 1.191 total


 exit code : 0

Sources

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