how to check if files exist in linux code example

Example 1: .sh script: check if file exist

#!/bin/bash
if [ -e x.txt ]
then
    echo "ok"
else
    echo "nok"
fi

Example 2: .sh script: check if file exist

# The most readable option when checking whether a file exist or not is
# to use the test command or the old '[' or the new '[[' in combination
# with the if statement.
# Any of the snippets below will check whether the /etc/resolv.conf file
# exists:

FILE=/etc/resolv.conf
if test -f "$FILE"; then
    echo "$FILE exist"
fi

# or

FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
    echo "$FILE exist"
fi

# or

FILE=/etc/resolv.conf
if [[ -f "$FILE" ]]; then
    echo "$FILE exist"
fi