[string] How to test if string exists in file with Bash?

I have a file that contains directory names:

my_list.txt :

/tmp
/var/tmp

I'd like to check in Bash before I'll add a directory name if that name already exists in the file.

Slightly similar to other answers but does not fork cat and entries can contain spaces

contains() {
    [[ " ${list[@]} " =~ " ${1} " ]] && echo 'contains' || echo 'does not contain'
}

IFS=$'\r\n' list=($(<my_list.txt))

so, for a my_list.txt like

/tmp
/var/tmp
/Users/usr/dir with spaces

these tests

contains '/tmp'
contains '/bin'
contains '/var/tmp'
contains '/Users/usr/dir with spaces'
contains 'dir with spaces'

return

exists
does not exist
exists
exists
does not exist

A grep-less solution, works for me:

MY_LIST=$( cat /path/to/my_list.txt )



if [[ "${MY_LIST}" == *"${NEW_DIRECTORY_NAME}"* ]]; then
  echo "It's there!"
else
echo "its not there"
fi

based on: https://stackoverflow.com/a/229606/3306354

Simpler way:

if grep "$filename" my_list.txt > /dev/null
then
   ... found
else
   ... not found
fi

Tip: send to /dev/null if you want command's exit status, but not outputs.

The @Thomas's solution didn't work for me for some reason but I had longer string with special characters and whitespaces so I just changed the parameters like this:

if grep -Fxq 'string you want to find' "/path/to/file"; then
    echo "Found"
else
    echo "Not found"
fi

Hope it helps someone

if grep -q "$Filename$" my_list.txt
   then
     echo "exist"
else 
     echo "not exist"
fi

grep -E "(string)" /path/to/file || echo "no match found"

-E option makes grep use regular expressions

I was looking for a way to do this in the terminal and filter lines in the normal "grep behaviour". Have your strings in a file strings.txt:

string1
string2
...

Then you can build a regular expression like (string1|string2|...) and use it for filtering:

cmd1 | grep -P "($(cat strings.txt | tr '\n' '|' | head -c -1))" | cmd2

Edit: Above only works if you don't use any regex characters, if escaping is required, it could be done like:

cat strings.txt | python3 -c "import re, sys; [sys.stdout.write(re.escape(line[:-1]) + '\n') for line in sys.stdin]" | ...

My version using fgrep

  FOUND=`fgrep -c "FOUND" $VALIDATION_FILE`
  if [ $FOUND -eq 0 ]; then
    echo "Not able to find"
  else
    echo "able to find"     
  fi  

Here's a fast way to search and evaluate a string or partial string:

if grep -R "my-search-string" /my/file.ext
then
    # string exists
else
    # string not found
fi

You can also test first, if the command returns any results by running only:

grep -R "my-search-string" /my/file.ext

Regarding the following solution:

grep -Fxq "$FILENAME" my_list.txt

In case you are wondering (as I did) what -Fxq means in plain English:

• F: Affects how PATTERN is interpreted (fixed string instead of a regex)
• x: Match whole line
• q: Shhhhh... minimal printing

From the man file:

-F, --fixed-strings
    Interpret  PATTERN  as  a  list of fixed strings, separated by newlines, any of which is to be matched.
    (-F is specified by POSIX.)
-x, --line-regexp
    Select only those matches that exactly match the whole line.  (-x is specified by POSIX.)
-q, --quiet, --silent
    Quiet; do not write anything to standard output.  Exit immediately with zero status  if  any  match  is
          found,  even  if  an error was detected.  Also see the -s or --no-messages option.  (-q is specified by
          POSIX.)

Easiest and simplest way would be:

isInFile=$(cat file.txt | grep -c "string")


if [ $isInFile -eq 0 ]; then
   #string not contained in file
else
   #string is in file at least once
fi

grep -c will return the count of how many times the string occurs in the file.

If I understood your question correctly, this should do what you need.

1. you can specifiy the directory you would like to add through $check variable
2. if the directory is already in the list, the output is "dir already listed"
3. if the directory is not yet in the list, it is appended to my_list.txt

In one line: check="/tmp/newdirectory"; [[ -n $(grep "^$check\$" my_list.txt) ]] && echo "dir already listed" || echo "$check" >> my_list.txt

If you just want to check the existence of one line, you do not need to create a file. E.g.,

if grep -xq "LINE_TO_BE_MATCHED" FILE_TO_LOOK_IN ; then
  # code for if it exists
else
  # code for if it does not exist
fi  

grep -Fxq "String to be found" | ls -a

• grep will helps you to check content
• ls will list all the Files

Three methods in my mind:

1) Short test for a name in a path (I'm not sure this might be your case)

ls -a "path" | grep "name"

2) Short test for a string in a file

grep -R "string" "filepath"

3) Longer bash script using regex:

#!/bin/bash

declare file="content.txt"
declare regex="\s+string\s+"

declare file_content=$( cat "${file}" )
if [[ " $file_content " =~ $regex ]] # please note the space before and after the file content
    then
        echo "found"
    else
        echo "not found"
fi

exit

This should be quicker if you have to test multiple string on a file content using a loop for example changing the regex at any cicle.