Ubuntu – Run the bash script every time when command lines are executed

bashcommand lineexecute-commandscripts

I am a new Ubuntu/Linux user, I would like to ask a question as my title above.

For example, I have a bash file ./script, I would like to make it run automatically when I type any command line. Once I execute command line pwd then the ./script will be executed. Once I type the next command line ls -la then the ./script will be executed again.

Best Answer

You need to set PROMPT_COMMAND variable. From man bash:

PROMPT_COMMAND
              If set, the value is executed as a command prior to
              issuing each primary prompt.

For example, this will write current date into /tmp/PC every time a command is executed:

 $ PROMPT_COMMAND="date > /tmp/PC"

xtrace

You could set the xtrace option (commonly used for debugging shell scripts) before running the command (no need to use command substitution). Also, don’t forget to unset the option afterwards.

set -x
some_command
set +x

Example:

$ set -x; sleep 2 && echo fin; set +x
+ sleep 2
+ echo fin
fin
+ set +x

echo

If you find the xtrace output to be too cluttered, you could simply echo the name of the command beforehand:

echo some_command
some_command

Bash Scripts – How to Run Executable Bash Script with Sudo Privileges

Read man sudoers - it will let you grant passwordless access to a single command. Read man visudo, too.

From the man page:

  PASSWD and NOPASSWD

   By default, sudo requires that a user authenticate him or herself before running a
   command.  This behavior can be modified via the NOPASSWD tag.  Like a Runas_Spec, the
   NOPASSWD tag sets a default for the commands that follow it in the Cmnd_Spec_List.
   Conversely, the PASSWD tag can be used to reverse things.  For example:

   ray     rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm

   would allow the user ray to run /bin/kill, /bin/ls, and /usr/bin/lprm as root on the
   machine rushmore without authenticating himself.  If we only want ray to be able to run
   /bin/kill without a password the entry would be:

   ray     rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm

   Note, however, that the PASSWD tag has no effect on users who are in the group specified
   by the exempt_group option.

Also, I'll note that "making an existing bash script run as root" is the beginning of many very sad security tales.

Rather than making the script run as root, allow your user passwordless access to the ( full path of ) the 2 commands in your script.

Best Answer

Related Solutions

Ubuntu – Display output of command executed in bash as it is executing

xtrace

echo

Bash Scripts – How to Run Executable Bash Script with Sudo Privileges

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