How to execute a shell script from C in Linux

Question

How can I execute a shell script from C in Linux

User · Answer

You can use system   system   usr local bin foo sh      This will block while executing it using sh -c  then return the status code

User · Answer

A simple way is        include  lt stdio h gt   include  lt stdlib h gt     define SHELLSCRIPT      bin bash  n  echo   hello    n  echo   how are you    n  echo   today    n      Also you can write using char array without using MACRO     You can do split it with many strings finally concatenate    and send to the system concatenated string       int main         puts  Will execute sh with the following script          puts SHELLSCRIPT       puts  Starting now         system SHELLSCRIPT        it will run the script inside the c code       return 0      Say thanks to Yoda  http   www unix com programming 216190-putting-bash-script-c-program html

User · Answer

I prefer fork   execlp for  more fine-grade  control as doron mentioned  Example code shown below   Store you command in a char array parameters  and malloc space for the result   int fd 2   pipe fd   if    childpid   fork        -1      fprintf stderr   FORK failed       return 1    else if  childpid    0       close 1      dup2 fd 1   1      close fd 0       execlp   bin sh    bin sh   -c  parameters NULL     wait NULL   read fd 0   result  RESULT SIZE   printf   s n  result

User · Answer

It depends on what you want to do with the script  or any other program you want to run    If you just want to run the script system is the easiest thing to do  but it does some other stuff too  including running a shell and having it run the command   bin sh under most  nix    If you want to either feed the shell script via its standard input or consume its standard output you can use popen  and pclose  to set up a pipe   This also uses the shell   bin sh under most  nix  to run the command   Both of these are library functions that do a lot under the hood  but if they don t meet your needs  or you just want to experiment and learn  you can also use system calls directly   This also allows you do avoid having the shell   bin sh  run your command for you   The system calls of interest are fork  execve  and waitpid   You may want to use one of the library wrappers around execve  type man 3 exec for a list of them    You may also want to use one of the other wait functions  man 2 wait has them all    Additionally you may be interested in the system calls clone and vfork which are related to fork   fork duplicates the current program  where the only main difference is that the new process gets 0 returned from the call to fork   The parent process gets the new process s process id  or an error  returned   execve replaces the current program with a new program  keeping the same process id    waitpid is used by a parent process to wait on a particular child process to finish   Having the fork and execve steps separate allows programs to do some setup for the new process before it is created  without messing up itself    These include changing standard input  output  and stderr to be different files than the parent process used  changing the user or group of the process  closing files that the child won t need  changing the session  or changing the environmental variables   You may also be interested in the pipe and dup2 system calls   pipe creates a pipe  with both an input and an output file descriptor    dup2 duplicates a file descriptor as a specific file descriptor  dup is similar but duplicates a file descriptor to the lowest available file descriptor

User · Answer

If you need more fine-grade control  you can also go the fork pipe exec route  This will allow your application to retrieve the data outputted from the shell script

User · Answer

If you re ok with POSIX  you can also use popen   pclose     include  lt stdio h gt   include  lt stdlib h gt   int main void       ls -al   grep   d       FILE  pp    pp   popen  ls -al    r      if  pp    NULL        while  1          char  line        char buf 1000         line   fgets buf  sizeof buf  pp         if  line    NULL  break        if  line 0      d   printf   s   line      line includes   n               pclose pp         return 0

[c] How to execute a shell script from C in Linux?

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