How to check if running as root in a bash script

Question

I m writing a script that requires root level permissions  and I want to make it so that if the script is not run as root  it simply echoes  Please run as root   and exits   Here s some pseudocode for what I m looking for   if  whoami    root    then echo  Please run as root     else  do stuff  fi  exit   How could I best  cleanly and securely  accomplish this  Thanks   Ah  just to clarify  the  do stuff  part would involve running commands that in-and-of themselves require root  So running it as a normal user would just come up with an error  This is just meant to cleanly run a script that requires root commands  without using sudo inside the script  I m just looking for some syntactic sugar

User · Answer

id -u is much better than whoami  since some systems like android may not provide the word root    Example     whoami whoami whoami  unknown uid 0

User · Answer

As  wrikken mentioned in his comments  id -u is a much better check for root   In addition  with proper use of sudo  you could have the script check and see if it is running as root   If not  have it recall itself via sudo and then run with root permissions   Depending on what the script does  another option may be to set up a sudo entry for whatever specialized commands the script may need

User · Answer

bin bash    GNU bash  version 4 3 46   Determine if the user executing this script is the root user or not    Display the UID echo  Your UID is   UID    if      UID   -eq 0   then     echo  You are root  else     echo  You are not root user  fi   Editor s note  If you don t need double brackets  use single ones for code portability

User · Answer

if      id -u  -ne 0      then echo  Please run as root    exit 1   fi   or  if     id -u  -ne 0      then echo  Please run as root    exit 1   fi

User · Answer

Check for root   ROOT UID 0     Root has  UID 0   if     UID  -eq   ROOT UID    then   echo  You are root   else   echo  You are just an ordinary user   fi  exit 0   Tested and running in root

User · Answer

0- Read official GNU Linux documentation  there are many ways to do it correctly   1- make sure you put the shell signature to avoid errors in interpretation       bin bash   2- this is my script     bin bash   if     EUID  gt  0     then   we can compare directly with this syntax    echo  Please run as root sudo    exit 1 else    do your stuff fi

User · Answer

There is a simple check for a user being root   The    stuff    syntax is the standard way of running a check in bash   error       printf   E 31m   echo       printf   E 0m     if     EUID -eq 0     then     error  Do not run this as the root user      exit 1 fi   This also assumes that you want to exit with a 1 if you fail  The error function is some flair that sets output text to red  not needed  but pretty classy if you ask me

User · Answer

One simple way to make the script only runnable by root is to start the script with the line        bin su root

User · Answer

Very simple way just put   if      whoami       root      then       you are root else       you are not root fi   The benefit of using this instead of id is that you can check whether a certain non-root user is running the command  too  eg   if      whoami       john      then       you are john else       you are not john fi

User · Answer

The problem using  id -u   EUID and whoami is all of them give false positive when I fake the root  for example    fakeroot  id    id -u 0  EUID    echo  EUID 0  whoami    whoami root  then a reliable and hacking way is verify if the user has access to the  root directory     ls  root   amp  gt  dev null  amp  amp  is root true    is root false  echo  is root

User · Answer

A few answers have been given  but it appears that the best method is to use is    id -u  If run as root  will return an id of 0    This appears to be more reliable than the other methods  and it seems that it return an id of 0 even if the script is run through sudo

User · Answer

In this answer  let it be clear  I presume the reader is able to read bash and POSIX shell scripts like dash  I believe there is not much to explain here since the highly voted answers do a good job of explaining much of it  Yet  if there is anything to explain further  don t hesitate to comment  I will do my best filling the gaps   Optimized all-round solution for performance and reliability  all shells compatible New solution    bool function to test if the user is root or not is user root          EUID -  id -u   -eq 0        Benchmark  save to file is user root  benchmark    ------------------------------------------------------------------------------                               is user root   benchmark                                                  quot Bash is fast while Dash is slow in this quot                                                  Language  POSIX shell script                                                    Copyright  2020 Vlastimil Burian                                                M il  info    vlastimilburian    cz                                                        License  GPL 3 0                                                                    Version  1 1                                     ------------------------------------------------------------------------------   readonly iterations 10000    intentionally  the file does not have executable bit  nor it has no shebang   to use it  just call the file directly with your shell interpreter like     bash is user root  benchmark   dash is user root  benchmark  is user root          EUID -  id -u   -eq 0       print time        date   quot  T  2N quot     print start       printf   s   Start       print time    print finish      printf   s   Finish      print time     printf   s n      is user root        print start                     i 1  while    i -lt  iterations    do     is user root     i    i   1   done  print finish  Examples of use and duration    dash is user root  benchmark     is user root      Start    03 14 04 81 Finish   03 14 13 29    bash is user root  benchmark     is user root      Start    03 16 22 90 Finish   03 16 23 08    Explanation Since it is multitude times faster to read the  EUID standard bash variable  the effective user ID number  than executing id -u command to POSIX-ly find the user ID  this solution combines both into a nicely packed function  If  and only if  the  EUID is for any reason not available  the id -u command will get executed  ensuring we get the proper return value no matter the circumstances   Why I post this solution after so many years the OP has asked Well  if I see correctly  there does seem to be a missing piece of code above  You see  there are many variables which have to be taken into account  and one of them is combining performance and reliability   Portable POSIX solution   Example of usage of the above function    bin sh    bool function to test if the user is root or not  POSIX only  is user root        quot   id -u  quot  -eq 0       if is user root  then     echo  You are the almighty root       exit 0   implicit  here it serves the purpose to be explicit for the reader else     echo  You are just an ordinary user    gt  amp 2     exit 1 fi   Conclusion As much as you possibly don t like it  the Unix   Linux environment has diversified a lot  Meaning there are people who like bash so much  they don t even think of portability  POSIX shells   Others like me prefer the POSIX shells  It is nowadays a matter of personal choice and needs

User · Answer

try the following code   if      id -u       0     then     echo  Sorry  you are not root       exit 1 fi   OR  if    id -u      0     then     echo  Sorry  you are not root       exit 1 fi

User · Answer

The  EUID environment variable holds the current user s UID  Root s UID is 0  Use something like this in your script   if     EUID  -ne 0     then echo  Please run as root    exit fi   Note  If you get 2     Illegal number  check if you have    bin sh at the top and change it to    bin bash

User · Answer

If the script really requires root access then its file permissions should reflect that  Having a root script executable by non-root users would be a red flag  I encourage you not to control access with an if check   chown root root script sh chmod u rwx go r script sh

User · Answer

Check if you are root and quit if you are not   if   EUID    0    then     echo  Root or Sudo  Required for script     basename  0         exit fi   Or in this example  try to create a directory in root location then try after rights were elevated   Check if you are root and if not elevate if possible      Fails to create these dirs  needs sudo  mkdir  test-dir-  basename  0  rmdir  test-dir-  basename  0   if   EUID    0    then     echo  Granting root privileges for script     basename  0         if    -t 1     then         sudo   0           else         exec 1 gt  output file         gksu   0           fi     exit fi echo  Root privileges granted       Creates Dirs as it now has rights mkdir  test-dir-  basename  0  rmdir  test-dir-  basename  0

User · Answer

As far as I know the correct way to check it is   if     id -u     0     then     echo  You are root  else     echo  You are NOT root  fi   See  Testing For Root  section here    http   linuxcommand org lc3 wss0080 php

User · Answer

In a bash script  you have several ways to check if the running user is root   As a warning  do not check if a user is root by using the root username  Nothing guarantees that the user with ID 0 is called root  It s a very strong convention that is broadly followed but anybody could rename the superuser another name   I think the best way when using bash is to use  EUID  from the man page   EUID   Expands to the effective user ID of the current  user   initialized        at shell startup   This variable is readonly    This is a better way than  UID which could be changed and not reflect the real user running the script   if     EUID    0     then     echo  Please run as root      exit fi   A way I approach that kind of problem is by injecting sudo in my commands when not run as root  Here is an example   SUDO    if     EUID    0     then     SUDO  sudo  fi  SUDO a command   This ways my command is run by root when using the superuser or by sudo when run by a regular user   If your script is always to be run by root  simply set the rights accordingly  0500

[bash] How to check if running as root in a bash script

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