How to Check a File Exists and Execute a Command If Not

How can I check a file exists and execute a command if not?

[ -f /tmp/filename.pid ] || python daemon.py restart

-f checks if the given path exists and is a regular file (just -e checks if the path exists)

the [] perform the test and returns 0 on success, 1 otherwise

the || is a C-like or, so if the command on the left fails, execute the command on the right.

So the final statement says, if /tmp/filename.pid does NOT exist then start the daemon.

How to check if a file exists from inside a batch file

if exist <insert file name here> (
    rem file exists
) else (
    rem file doesn't exist
)

Or on a single line (if only a single action needs to occur):

if exist <insert file name here> <action>

for example, this opens notepad on autoexec.bat, if the file exists:

if exist c:\autoexec.bat notepad c:\autoexec.bat

How to check if a file exists in a shell script

You're missing a required space between the bracket and -e:

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

How to verify if a file exists in a batch file?

You can use IF EXIST to check for a file:

IF EXIST "filename" (
  REM Do one thing
) ELSE (
  REM Do another thing
)

If you do not need an "else", you can do something like this:

set __myVariable=
IF EXIST "C:\folder with space\myfile.txt" set __myVariable=C:\folder with space\myfile.txt
IF EXIST "C:\some other folder with space\myfile.txt" set __myVariable=C:\some other folder with space\myfile.txt
set __myVariable=

Here's a working example of searching for a file or a folder:

REM setup

echo "some text" > filename
mkdir "foldername"

REM finds file    

IF EXIST "filename" (
  ECHO file filename exists
) ELSE (
  ECHO file filename does not exist
)

REM does not find file

IF EXIST "filename2.txt" (
  ECHO file filename2.txt exists
) ELSE (
  ECHO file filename2.txt does not exist
)

REM folders must have a trailing backslash    

REM finds folder

IF EXIST "foldername\" (
  ECHO folder foldername exists
) ELSE (
  ECHO folder foldername does not exist
)

REM does not find folder

IF EXIST "filename\" (
  ECHO folder filename exists
) ELSE (
  ECHO folder filename does not exist
)

How do I check if file exists in Makefile so I can delete it?

The second top answer mentions ifeq, however, it fails to mention that this ifeq must be at the same indentation level in the makefile as the name of the target, e.g., to download a file only if it doesn't currently exist, the following code could be used:

download:
ifeq (,$(wildcard ./glob.c))
    curl … -o glob.c
endif

# THIS DOES NOT WORK!
download:
    ifeq (,$(wildcard ./glob.c))
        curl … -o glob.c
    endif

short way to check (one liner) if a file exists or not

Try this:

[ -f file ] && echo 1 || echo 0

How to execute certain commands if a file does NOT exist?

You can use this:

if [ ! -e "$file" ]; then
       touch file
else
        ...
fi

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