This is giving just the output of ls:
String[] cmd={"bash","-c","ls","-l"}:
ProcessBuilder pb=new ProcessBuilder(cmd);
Whereas this is giving long listing output properly:
String[] cmd={"bash","-c","ls -l"};
3 Answers
In the first code snippet, the -l option is being passed as an argument to bash, and not to ls. Bash interprets the -l option as specifying that it should behave as a 'login' shell.
The argument after -c should include the whole bash script (spaces included) that you want to be executed, so the second code snippet is correct.
2 Comments
HelloWorld
Oh okay. Thank you. But what if I want to dynamically display files using cat command. An example scenario would be when I want to pass file names in a loop for display.
Martin Ellis
If you want to invoke
cat once with multiple parameters, then you could use a StringBuilder and for loop to build up the command line into a single string (with spaces between file names). That could be appended onto the string "cat ", and used for the command line argument following -c.The former passes two option flags to bash: -c with argument ls, and -l which according to the manpage causes bash to act as a login shell.
The second passes one option flag, -c, which the argument ls -l as a single string.
1 Comment
HelloWorld
Oh okay. Thank you. But what if I want to dynamically display files using cat command. An example scenario would be when I want to pass file names in a loop for display
String[] cmd={"bash","-c","ls -l"}:
ProcessBuilder pb=new ProcessBuilder(cmd);
The arguements are to bash, so if you want bash to interpert your "command" via "bash", "-c", ... then the next item needs to be your entire command, aka "ls -l".
Bash will then parse up the "command" and the -l will be sent as a parameter to "ls". Currently it is a parameter to "bash", which is why you're not getting the results you desire.
{ "ls", "-l" }