Issuing a Here Document as a Single Line Command

UNIX for Advanced & Expert Users
1

How can I run a here document on just one line? I ask, because I need to issue it from C++ as a system() or similar command and for security reasons I don't want to write out a shell script file from the program and run it.

For example, how could I write:

passwd test <<EOF
n3wp3ss
n3wp3ss
EOF

as s single command? I've tried semicolons and they don't work for this.

Thanks in advance.

Brandon

2

will this do?

cmd=sprintf("passwd test <<EOF\nn3wp3ss\nn3wp3ss\nEOF")
system(cmd)
3

What security reasons are these? A plaintext password is a plaintext password no matter how you cut it. Shoving it inside a C program does not help. Just run strings on it and bam, they have your password.

You can protect it with chmod -r, of course. But that's only protection from lower users and not any protection from anyone who needs to run the program. And you could've done that for a shell script anyway.

Since you're doing it in C, you can put newlines wherever you please with \n, effectively making a multi-line string. Also note that if you put "two" "strings" in a row, they become "twostrings", so you can organize it nicely by line and still have it one giant string.

system("cat <<EOF\n"
        "This is a here document\n"
        "being executed in system()\n"
        "EOF\n");
4

Thanks.