Check Whether a User Exists

Question

I want to create a script to check whether a user exists  I am using the logic below     getent passwd test  gt   dev null 2 amp  gt 1   echo    0   getent passwd test1  gt   dev null 2 amp  gt 1   echo    2   So if the user exists  then we have success  else the user does not exist  I have put above command in the bash script as below      bin bash  getent passwd  1  gt   dev null 2 amp  gt 1  if      -eq 0    then     echo  yes the user exists  else     echo  No  the user does not exist  fi   Now  my script always says that the user exists no matter what     sh passwd sh test yes the user exists   sh passwd sh test1 yes the user exists   sh passwd sh test2 yes the user exists   Why does the above condition always evaluate to be TRUE and say that the user exists   Where am I going wrong   UPDATE   After reading all the responses  I found the problem in my script  The problem was the way I was redirecting getent output  So I removed all the redirection stuff and made the getent line look like this   getent passwd  user   gt   dev null   Now my script is working fine

User · Answer

By far the simplest solution  if id -u  quot  user quot   gt  dev null 2 gt  amp 1  then     echo  user exists  else     echo  user missing  fi  The  gt  dev null 2 gt  amp 1 can be shortened to  amp  gt  dev null in Bash

User · Answer

Actually I cannot reproduce the problem  The script as written in the question works fine  except for the case where  1 is empty   However  there is a problem in the script related to redirection of stderr  Although the two forms  amp  gt  and  gt  amp  exist  in your case you want to use  gt  amp   You already redirected stdout  that s why the form  amp  gt  does not work  You can easily verify it this way   getent  etc passwd username  gt  dev null 2 amp  gt 1 ls   You will see a file named 1 in the current directory  You want to use 2 gt  amp 1 instead  or use this   getent  etc passwd username  amp  gt  dev null   This also redirects stdout and stderr to  dev null   Warning Redirecting stderr to  dev null might not be such a good idea  When things go wrong  you will have no clue why

User · Answer

Depending on your shell implementation  e g  Busybox vs  grown-up  the   operator might start a process  changing      Try  getent passwd  1  gt   dev null 2 amp  gt 1 RES     if    RES -eq 0    then     echo  yes the user exists  else     echo  No  the user does not exist  fi

User · Answer

Create system user some user if it doesn t exist  if      getent passwd some user           then     sudo adduser --no-create-home --force-badname --disabled-login --disabled-password --system some user fi

User · Answer

I was using it in that way   if     getent passwd  user      then         echo user  user exists else         echo user  user doesn  t exists fi

User · Answer

Login to the server  grep  username    etc passwd This will display the user details if present

User · Answer

I suggest to use id command as it tests valid user existence wrt passwd file entry which is not necessary means the same   if    id -u  USER TO CHECK 2 gt  dev null    echo -1  -ge 0    then  echo FOUND fi   Note  0 is root uid

User · Answer

Script to Check whether Linux user exists or not  Script To check whether the user exists or not      bin bash USER NAME bakul cat  etc passwd   grep   USER NAME   gt  dev null 2 gt  amp 1 if      -eq 0     then     echo  User Exists  else     echo  User Not Found  fi

User · Answer

Below is the script to check the OS distribution and create User if not exists and do nothing if user exists      bin bash    Detecting OS Ditribution if   -f  etc os-release    then        etc os-release     OS  NAME elif type lsb release  gt  dev null 2 gt  amp 1  then OS   lsb release -si  elif   -f  etc lsb-release    then        etc lsb-release     OS  DISTRIB ID else     OS   uname -s  fi   echo   OS    user   cat  etc passwd   egrep -e ansible   awk -F        print  1       Adding User based on The OS Distribution  if     OS     Red Hat             OS     Amazon Linux             OS     CentOS         amp  amp       user      ansible     then  sudo useradd ansible  elif     OS     Ubuntu    amp  amp      user      ansible     then sudo adduser --disabled-password --gecos    ansible else   echo   user is already exist on  OS   exit fi

User · Answer

You can also check user by id command  id -u name gives you the id of that user  if the user doesn t exist  you got command return value     1 And as other answers pointed out  if all you want is just to check if the user exists  use if with id directly  as if already checks for the exit code  There s no need to fiddle with strings        or      if id  quot  1 quot   amp  gt  dev null  then     echo  user found  else     echo  user not found  fi   no need to use -u as you re discarding the output anyway  Also  if you turn this snippet into a function or script  I suggest you also set your exit code appropriately     bin bash user exists    id  quot  1 quot   amp  gt  dev null      silent  it just sets the exit code if user exists  quot  1 quot   code     then    use the function  save the code     echo  user found  else     echo  user not found   gt  amp 2    error messages should go to stderr fi exit  code    set the exit code  ultimately the same set by  id

User · Answer

user infomation is stored in  etc passwd  so you can use  grep  usename   etc passwd  to check if the username exist  meanwhile you can use  id  shell command  it will print the user id and group id  if the user does not exist  it will print  no such user  message

User · Answer

This is what I ended up doing in a Freeswitch bash startup script      Check if user exists if   id -u  FS USER  gt   dev null 2 gt  amp 1  then     echo  The user does not exist  execute below commands to crate and try again       echo    root sh1    adduser --home  usr local freeswitch  --shell  bin false --no-create-home --ingroup daemon --disabled-password --disabled-login  FS USER      echo             echo    root sh1    chown freeswitch daemon  usr local freeswitch  -R      exit 1 fi

User · Answer

I like this nice one line solution   getent passwd username  gt   dev null 2 amp  gt 1  amp  amp  echo yes    echo no   and in script      bin bash  if     1           then         getent passwd  1  gt   dev null 2 amp  gt 1  amp  amp   echo yes  exit 0      echo no  exit 2  else         echo  missing username          exit -1 fi   use    mrfish yoda       u exists sh root yes  mrfish yoda     echo    0   mrfish yoda       u exists sh missing username  mrfish yoda     echo    255   mrfish yoda       u exists sh aaa no  mrfish indegy     echo    2

User · Answer

There s no need to check the exit code explicitly  Try  if getent passwd  1  gt   dev null 2 gt  amp 1  then     echo  yes the user exists  else     echo  No  the user does not exist  fi   If that doesn t work  there is something wrong with your getent  or you have more users defined than you think

User · Answer

Why don t you simply use  grep -c   username    etc passwd   It will return 1  since a user has max  1 entry  if the user exists and 0 if it doesn t

User · Answer

Using sed   username  alice  if    sed -n     username p   etc passwd    then     echo  User   username  already exists  else     echo  User   username  doesn t exist  fi

User · Answer

Late answer but finger also shows more information on user    sudo apt-get finger    finger   username

[bash] Check Whether a User Exists

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