bash if statement to detect blank text

Question

Hello i am currently trying to make an if statement within shell script to detect if the user has no inputted any text.

i would like if the user hasnt entered anythign or if what they entered is invalid to echo and alert until they type in something correct.

here is what i have so far

echo "Current Address books "
        ls -R |grep .txt
        echo "--------------------------------------------------------------------"
        echo -n  "Please Enter the file you want to search in: "
        read fileName
        book=$fileName
        if [ $fileName == "" ]
        then
                echo "Please Enter some Text "
        else
                echo -n "Please Enter a name: "
        read search

        grep -i $search $fileName

        if grep -q "$search" "$fileName";
        then
                echo "Found!"
        else
                echo "Not Found!"
        fi

fi

gniourf_gniourf · Accepted Answer · 2014-04-20 17:49:20Z

1

Something like this?

#!/bin/bash

echo "Current Address books "
find -name '*.txt' -type f -exec bash -c 'printf "%s\n" "${@#./}"' _ {} + # Don't parse the output of ls
printf -v spacesep "%68s"; printf '%s\n' "${spacesep// /-}"
fileName=
while [[ -z $fileName ]]; do
    read -rep "Please Enter the file you want to search in: " fileName
    book=$fileName # Is this variable used?
    # Check that the file is really a file
    if [[ -n $fileName ]] && [[ ! -f $fileName ]]; then
      echo "Not a file, try again"
      fileName=
    fi
done
search=
while [[ -z $search ]]; do
    read -rep "Please Enter a name: " search
    grep -i -- "$search" "$fileName"
done
if grep -qi -- "$search" "$fileName"; then
   echo "Found!"
else
   echo "Not Found!"
fi

Bonus. With the -e switch to read you have readline editing capabilities, and tab completion on files. Wooow!

edited Apr 20, 2014 at 17:49

answered Apr 20, 2014 at 17:44

gniourf_gniourf

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3 Comments

user258030 Over a year ago

can you explain what 'printf "%s\n" "${@#./}"' does to me?

gniourf_gniourf Over a year ago

@user258030 Without this, the output of find will have leading ./ in front of every file name. The snippet "${@#./}" expands to all positional parameters with leading ./ removed. So printf "%s\n" "${@#./}" prints, one per line, the positional parameters with leading ./ removed.

user258030 Over a year ago

Thanks that was a complex yet perfect solution to what i needed

anubhava · Accepted Answer · 2014-04-20 17:18:23Z

1

You can use -z "$var" notation:

if [ -z "$fileName" ]; then
   echo "Please Enter some Text "
else
   read -p "Please Enter a name: " search
fi

to check if string length is zero.

Alternatively you can do this check using quoted variable name:

if [ "$fileName" == "" ]; then
   echo "Please Enter some Text "
else
   read -p "Please Enter a name: " search
fi

answered Apr 20, 2014 at 17:18

anubhava

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Comments

user3554425 · Accepted Answer · 2014-04-20 17:28:48Z

1

You can use a control loop

until [  $fileName != "" ]; do
     echo "Please Enter some Text " ;
     read -p "Please Enter a name: " fileName ;
done

answered Apr 20, 2014 at 17:28

user3554425

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