if condition to check file or directory exists

-e: Returns true value, if file exists

-f: Return true value, if file exists and regular file

-r: Return true value, if file exists and is readable

-w: Return true value, if file exists and is writable

-x: Return true value, if file exists and is executable

-d: Return true value, if exists and is a directory

File Testing
-b filename – Block special file
-c filename – Special character file
-d directoryname – Check for directory existence
-e filename – Check for file existence
-f filename – Check for regular file existence not a directory
-G filename – Check if file exists and is owned by effective group ID.
-g filename – true if file exists and is set-group-id.
-k filename – Sticky bit
-L filename – Symbolic link
-O filename – True if file exists and is owned by the effective user id.
-r filename – Check if file is a readable
-S filename – Check if file is socket
-s filename – Check if file is nonzero size
-u filename – Check if file set-user-id bit is set
-w filename – Check if file is writable
-x filename – Check if file is executable

example script,

if a file does not exist

if [ ! -f /tmp/rmohan.txt ]; then
echo “File not found!”
fi

#!/bin/bash
FILE=$1

if [ ! -f “$FILE” ]
then
echo “File $FILE does not exists”
fi

if [[ ! -a $FILE ]]; then
echo “$FILE does not exist!”
fi

Also, it’s possible that the file is a broken symbolic link, or a non-regular file,

like e.g. a socket, device or fifo. If you want to catch that you should:

if [[ ! -a $FILE ]]; then
if [[ -L $FILE ]]; then
echo “$FILE is a broken symlink!”
else
echo “$FILE does not exist!”
fi
fi

To reverse a test, use “!”. That is equivalent to the “not” logical operator in other languages. Try this:

if [ ! -f /tmp/test.txt ];
then
echo “File not found!”
fi
Or written in a slightly different way:

if [ ! -f /tmp/test.txt ]
then echo “File not found!”
fi
Or you could use:

if ! [ -f /tmp/test.txt ]
then echo “File not found!”
fi
Or, presing all together:

if ! [ -f /tmp/test.txt ]; then echo “File not found!”; fi
Which may be written (using then “and” operator: &&) as:

[ ! -f /tmp/test.txt ] && echo “File not found!”
Which looks shorter like this:

[ -f /tmp/test.txt ] || echo “File not found!”

echo “entre file”

read a

if [ -s /home/rmohan/$a ]

then

echo “yes file is there ”

else

echo “soryy file is not there”

fi

if [ true ]
then
# do something here
fi
Very important: Make sure you leave spaces around the bracket characters.

I’ll show more detailed tests as we go along.

Linux shell file-related tests
To perform tests on files use the following comparison operators:

-d file Test if file is a directory
-e file Test if file exists
-f file Test if file is an ordinary file
-r file Test if file is readable
-w file Test if file is writable
-x file Test if file is executable