Interacting with the enviroment
From Organic Design wiki
Enviroment variables
It's quite simple to read and write environment variables from C:
char *envvar; if(envvar = getenv("FOO")) printf( "FOO=%s\n", envvar ); putenv("FOO=bar");
When you call a child process a copy of the enviroment is passed to this process. However, if the process changes enviroment variables, these changes will be lost once the process terminates.
The parent C program:
putenv("FOO=bar"); system("sh printenv"); if(envvar = getenv("FOO")) printf( "FOO=%s\n", envvar );
Executes a shell script (printenv) with system()
echo "printenv: $FOO" FOO=bar2
The resulting output is:
printenv: bar FOO=bar
Pipes
The output of this program is something like:
Begin pipe(): 3 4 fork() pid 19260 wait() returned with status 0 read(): fetched 83 bytes hello world! FOO=foo was set by the child Child changing foo FOO=child changed foo Parent: FOO=foo was set by the parent
bash
To connect to a bash shell you can simply do:
cat > bash
This will create an asynchronous connection to the bash process.