I want to run something like
cat file.tar | base64 | myprogram -c "| base64 -d | tar -zvt "
I use execlp
to run the process.
When i try to run something like cat
it works, but if i try to run base64 -d | tar -zvt
it doesn't work.
I looked at the bash commands and I found out that I can run bash and tell him to run other programs. So it's something like:
execlp ("bash", "-c", "base64 -d | tar -zvt", NULL);
If I run it on the terminal, it works well, but using the execlp
it dont work.
If I use execlp("cat", "cat", NULL)
it works.
Someone knows how to use the -c
param on execlp to execute multiple "programs"?
I cant use system because i use pipe and fork.
Now i noticed, if i try to use execlp("bash", "bash", "-c", "base64", NULL)... nothing happens. If i use execlp("cat", NULL) it's ok.. I'm writing to the stdin... i don't know if its the problem with the bash -c base64.. because if i run on the terminal echo "asd" | bash -c "cat" it goes well
The first "argument" is what becomes argv[0]
, so you should call with something like:
execlp("bash", "bash", "-c", "base64 -d | tar -zvt", NULL);
Edit A small explanation what the above function does: The exec
family of functions executes a program. In the above call the program in question is "bash" (first argument). Bash, like all other programs, have a main
function that is the starting point of the program. And like all other main
functions, the one in Bash receives two arguments, commonly called argc
and argv
. argv
is an array of zero-terminated strings, and argc
is the number of entries in the argv
array. argc
will always be at least 1, meaning that there is always one entry at argv[0]
. This first entry is the "name" of the program, most often the path of the program file. All other program arguments on the command line is put into argv[1]
to argv[argc - 1]
.
What execlp
does is use the first argument to find the program to be executed, and all the other arguments will be put into the programs argv
array in the order they are given. This means that the above call to execlp
will call the program "bash" and set the argv
array of Bash to this:
argv[0] = "bash"
argv[1] = "-c"
argv[2] = "base64 -d | tar -zvt"
Also, argc
of Bash will be set to 3.
If the second "bash"
is changed to "foo"
, then argv[0]
of Bash will be set to "foo"
as well.
I hope this clears it up a little bit.
来源:https://stackoverflow.com/questions/8819135/execlp-multiple-programs