Checking it see if a file exists in a script

So I have a filename bobv1.txt, and I don't want to manually check to see if bobv2.txt is on the site. On the site bobv1.txt will be replaced by bobv2.txt. I have downloaded the the html page and determined the full download path of bobvX.txt and I know were the file is in my file system. How can I tell if the file is already on my file system? I need this to work for all subsequent versions.

2 Answers

If you need a shell script then you can use this:

#!/bin/bash
file="$1"
if [ -f "$file" ]; then echo "File $file exists."
else echo "File $file does not exist."
fi

You can run it like this:

bash test.sh /tmp/bobv2.txt

There's plenty of ways to perform a check on whether or not a file exists.

• use test command ( aka [ ) to do [ -f /path/to/file.txt ]

• use redirection to attempt to open file ( note that this isn't effective if you lack permissions to read the said file)

  $ bash -c 'if < /bin/echo ;then echo "exists" ; else echo "does not exist" ; fi'
  exists
  $ bash -c 'if < /bin/noexist ;then echo "exists" ; else echo "does not exist" ; fi'
  $ bash: /bin/noexist: No such file or directory
  does not exist

  or with silencing the error message:

  $ 2>/dev/null < /etc/noexist || echo "nope"
  nope

• use external program such as stat

  $ if ! stat /etc/noexist 2> /dev/null; then echo "doesn't exist"; fi
  doesn't exist

  or find command:

  $ find /etc/passwd
  /etc/passwd
  $ find /etc/noexist
  find: ‘/etc/noexist’: No such file or directory