How to check if a file exists in a shell script

Question

I d like to write a shell script which checks if a certain file  archived sensor data json  exists  and if so  deletes it  Following http   www cyberciti biz tips find-out-if-file-exists-with-conditional-expressions html  I ve tried the following    -e archived sensor data json   amp  amp  rm archived sensor data json   However  this throws an error   -e  command not found   when I try to run the resulting test controller script using the   test controller command  What is wrong with the code

User · Answer

If you re using a NFS   test  is a better solution  because you can add a timeout to it  in case your NFS is down   time timeout 3 test -f   nfs my nfs is currently down real    0m3 004s  lt  lt    timeout is taken into account user    0m0 001s sys     0m0 004s echo    124    lt   124 means the timeout has been reached   A    -e my file    construct will freeze until the NFS is functional again   if   -e  nfs my nfs is currently down    then echo  ok  else echo  ko    fi   lt no answer from the system  my session is  frozen  gt

User · Answer

Internally  the rm command must test for file existence anyway  so why add another test   Just issue  rm filename   and it will be gone after that  whether it was there or not  Use rm -f is you don t want any messages about non-existent files     If you need to take some action if the file does NOT exist  then you must test for that yourself   Based on your example code  this is not the case in this instance

User · Answer

Here is an alternative method using ls    ls x txt  amp  amp  echo yes     echo no   If you want to hide any output from ls so you only see yes or no  redirect stdout and stderr to  dev null    ls x txt  gt  gt   dev null 2 gt  amp 1  amp  amp  echo yes     echo no

User · Answer

The backdrop to my solution recommendation is the story of a friend who  well into the second week of  his first job  wiped half a build-server clean  So the basic task is to figure out if a file exists   and if so  let s delete it  But there are a few treacherous rapids on this river    Everything is a file  Scripts have real power only if they solve general tasks To be general  we use variables We often use -f force in scripts to avoid manual intervention And also love -r recursive to make sure we create  copy and destroy in a timely fashion    Consider the following scenario   We have the file we want to delete  filesexists json  This filename is stored in a variable   lt host gt    Documents thisfolderexists filevariable  filesexists json    We also hava a path variable to make things really flexible   lt host gt    Documents thisfolderexists pathtofile        lt host gt    Documents thisfolderexists ls  pathtofile  filesexists json  history20170728  SE-Data-API pem  thisfolderexists   So let s see if -e does what it is supposed to  Does the files exist    lt host gt    Documents thisfolderexists   -e  pathtofile  filevariable    echo     0   It does  Magic   However  what would happen  if the file variable got accidentally be evaluated to nuffin    lt host gt    Documents thisfolderexists filevariable      lt host gt    Documents thisfolderexists   -e  pathtofile  filevariable    echo     0   What  It is supposed to return with an error    And this is the beginning of the story how that entire  folder got deleted by accident  An alternative could be to test specifically for what we understand to be a  file    lt host gt    Documents thisfolderexists filevariable  filesexists json    lt host gt    Documents thisfolderexists test -f  pathtofile  filevariable  echo     0   So the file exists      lt host gt    Documents thisfolderexists filevariable      lt host gt    Documents thisfolderexists test -f  pathtofile  filevariable  echo     1   So this is not a file and maybe  we do not want to delete that entire directory  man test has the following to say   -b FILE         FILE exists and is block special  -c FILE         FILE exists and is character special  -d FILE         FILE exists and is a directory  -e FILE         FILE exists  -f FILE         FILE exists and is a regular file       -h FILE         FILE exists and is a symbolic link  same as -L

User · Answer

You re missing a required space between the bracket and -e      bin bash if   -e x txt   then     echo  ok  else     echo  nok  fi

[shell] How to check if a file exists in a shell script

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