One liner to check for file exists [duplicate]

Question

Objective: Check for presence of backup .tgz file containing today's date; output 1 for OK, 0 for no file.

I'm a sucker for one liners :) For example in PHP (and pretty much similar in Javascript), in various scenarios I like to do something like

<?php
echo (date("d")==1)?"Monday":"Not Monday";
?>

Is there similar syntax in Bash? I know how to check for presence of a regular file using -f FILENAME, I only want the command to print 1 or 0 :)

Answer 1

You can simply do this :

#to check if it's a regular file
[ -f "/you/file.file" ] && echo 1 || echo 0
#to check if a file exist
[ -e "/you/file.file" ] && echo 1 || echo 0

In shell this charater [ means test, -e if file exists ] end of test && if command return true execute the command after, || if command return false execute command after.
This should work in shell and bash

Answer 2

if [ ! -f /tmp/foo.txt ]; then echo "File not found!"; else echo "file found"; fi

Answer 3

With zsh:

(){echo $#} *"$(date +%Y-%m-%d)"*.tgz(DN)

Would output the number of files in the current directory whose name contains the current date in YYYY-mm-dd format and end in .tgz as a decimal number. Replace (DN) with (DN[1]) if you want only 0 or 1.

To use as the condition in an if statement, you can do:

if ()(($#)) *"$(date +%Y-%m-%d)"*.tgz(DN); then
   echo found
else
   echo none found
fi

In bash

the equivalent could be:

(shopt -s nullglob dotglob; set -- *"$(date +%Y-%m-%d)"*.tgz; echo "$#")

(replace "$#" with "$(($#>0))" to get 0 or 1).

and

if (shopt -s nullglob dotglob; set -- *"$(date +%Y-%m-%d)"*.tgz; (($#))); then
   echo found
else
   echo none found
fi

With ksh93:

(FIGNORE='@(.|..)'; set -- ~(N)*"$(date +%Y-%m-%d)"*.tgz; echo "$#")

and

if (FIGNORE='@(.|..)'; set -- ~(N)*"$(date +%Y-%m-%d)"*.tgz; (("$#"))); then...

POSIXly

ls -qA | grep -c "$(date +%Y-%m-%d).*\.tgz$"

for the count.

ls -qA | grep -q "$(date +%Y-%m-%d).*\.tgz$"; echo "$(($? == 0))"

for 0 or 1 and:

And:

if ls -qA | grep -q "$(date +%Y-%m-%d).*\.tgz$"; then...

Though the common wisdom is not to parse the output of ls, here with -q, we're making sure there's one file per line and the replacing of non-printable characters with ? shouldn't affect the greping for our pattern so it should be relatively safe.

You may see differences if the file names contain sequences of bytes that don't form valid characters. One advantage is that you'll get an error message if the current directory is no readable.

Answer 4

You can use this command:

test -e *$(date).tgz && echo 1 || echo 0

Answer 5

As yet another variant, if you knew the exact format of the filename you were looking for you could use

[ ! -f FILENAME ]; echo $?

or

echo `[ ! -f FILENAME ]` $?

however this couldn't cope with wildcards, so files ending in .tgz containing today's date would need something more complex, such as

echo $( for entry in *$(date --rfc-3339=date)*.tgz; do [ -f "$entry" ] && exit 1; done; exit 0 ) $?

Answer 6

I know you asked for Bash, but if you're looking for any command line program that will work, I recommend Python:

python -c "import os; exists = os.path.isfile('myFile.txt'); print(int(exists))"

Answer 7

ls filename 2> /dev/null && echo 1 || echo 0

Or, if you want it in a variable

EXISTS=$(ls filename 2> /dev/null && echo 1 || echo 0)