Native shebang: Difference between revisions

<lang c>#!/usr/local/bin/script_gcc.sh

#include <errno.h>

/* the actual shebang for C targets is:

#!/usr/local/bin/script_gcc.c

<lang c>#!/usr/local/bin/script_gcc.c

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

int main(int argc, char **argv, char **envp){

char ofs = '\0';

for(argv++; *argv; argv++){

if(ofs)putchar(ofs); else ofs=' ';

fwrite(*argv, strlen(*argv), 1, stdout);

}

putchar('\n');

exit(EXIT_SUCCESS);

}</lang>

'''Test Execution:'''

<pre>

$ ./echo.c Hello, world!

</pre>

'''Test Output:'''

<pre>

Hello, world!

</pre>

=={{header|UNIX Shell}}==

{{works with|Bourne Again SHell}}

Note: this '''Native shebang''' task does not exactly apply to [[bash]] because is interpretive, but as a skeleton template the following script is an example of how compiled languages can implement the shebang. Also: this bash code can be used to ''automatically'' compile the C code in /usr/local/bin/script_gcc.c above.

'''File: script_gcc.sh'''

<lang bash>#!/bin/bash

# Alternative:

#!/bin/bash /usr/local/bin/gcc_script.sh

# CACHE=No # to turn off caching...

# Note: this shell should be re-written in actual C! :-)

DIALECT=c # or cpp

CC="gcc"

COPTS="-lm -x $DIALECT"

IEXT=.$DIALECT

OEXT=.out

ENOENT=2

srcpath="$1"; shift # => "$@"

#basename="$(basename "$srcpath" ."$DIALECT")"

basename="$(basename "$srcpath")"

# Warning: current dir "." is in path, AND */tmp directories are common/shared

paths="$(dirname "$srcpath")

$HOME/bin

/usr/local/bin

.

$HOME/tmp

$HOME

$HOME/Desktop"

#/tmp

while read dirnamew; do

[ -w "$dirnamew" ] && break

done << end_here_is

$paths

end_here_is

compile(){

sed -n '2,$p' "$srcpath" | "$CC" $COPTS -o "$binpath" -

}

if [ "'$CACHE'" = "'No'" ]; then

binpath="$dirnamew/$basename-v$$$OEXT"

if compile; then

( sleep 0.1; exec rm "$binpath" ) & exec "$binpath" "$@"

fi

else

while read dirnamex; do

binpath="$dirnamex/$basename$OEXT"

if [ -x "$binpath" -a "$binpath" -nt "$srcpath" ];

then exec "$binpath" "$@"; fi

done << end_here_is

$paths

end_here_is

binpath="$dirnamew/$basename$OEXT"

if compile; then exec "$binpath" "$@"; fi

echo "$binpath: executable not available" 1>&2

exit $ENOENT

fi</lang>

'''Test Source File: echo.c'''

<lang c>#!/usr/local/bin/script_gcc.sh