85 lines
2.5 KiB
Text
85 lines
2.5 KiB
Text
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#!/bin/bash
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#
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# `sbang`: Run scripts with long shebang lines.
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#
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# Many operating systems limit the length of shebang lines, making it
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# hard to use interpreters that are deep in the directory hierarchy.
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# `sbang` can run such scripts, either as a shebang interpreter, or
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# directly on the command line.
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#
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# Usage
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# -----------------------------
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# Suppose you have a script, long-shebang.sh, like this:
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#
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# 1 #!/very/long/path/to/some/interpreter
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# 2
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# 3 echo "success!"
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#
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# Invoking this script will result in an error on some OS's. On
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# Linux, you get this:
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#
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# $ ./long-shebang.sh
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# -bash: ./long: /very/long/path/to/some/interp: bad interpreter:
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# No such file or directory
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#
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# On Mac OS X, the system simply assumes the interpreter is the shell
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# and tries to run with it, which is likely not what you want.
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#
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#
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# `sbang` on the command line
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# -----------------------------
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# You can use `sbang` in two ways. The first is to use it directly,
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# from the command line, like this:
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#
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# $ sbang ./long-shebang.sh
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# success!
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#
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#
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# `sbang` as the interpreter
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# -----------------------------
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# You can also use `sbang` *as* the interpreter for your script. Put
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# `#!/bin/bash /path/to/sbang` on line 1, and move the original
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# shebang to line 2 of the script:
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#
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# 1 #!/bin/bash /path/to/sbang
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# 2 #!/long/path/to/real/interpreter with arguments
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# 3
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# 4 echo "success!"
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#
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# $ ./long-shebang.sh
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# success!
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#
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# On Linux, you could shorten line 1 to `#!/path/to/sbang`, but other
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# operating systems like Mac OS X require the interpreter to be a
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# binary, so it's best to use `sbang` as a `bash` argument.
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# Obviously, for this to work, `sbang` needs to have a short enough
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# path that *it* will run without hitting OS limits.
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#
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#
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# How it works
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# -----------------------------
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# `sbang` is a very simple bash script. It looks at the first two
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# lines of a script argument and runs the last line starting with
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# `#!`, with the script as an argument. It also forwards arguments.
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#
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# First argument is the script we want to actually run.
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script="$1"
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# Search the first two lines of script for interpreters.
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lines=0
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while read line && ((lines < 2)) ; do
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if [[ "$line" = '#!'* ]]; then
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interpreter="${line#\#!}"
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fi
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lines=$((lines+1))
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done < "$script"
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# Invoke any interpreter found, or raise an error if none was found.
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if [ -n "$interpreter" ]; then
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exec $interpreter "$@"
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else
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echo "error: sbang found no interpreter in $script"
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exit 1
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fi
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