gcc build script (alias to 'g')

#!/bin/bash --norc

## script to build c-source files with gcc allowing minimal cli input. There are
#  two required arguments: an output file <ofile> and the c-source <file.c>. The
#  default usage is:
#
#   $ ./bgc.sh <ofile> <file.c>  (calls: gcc -Wall -o bin/<ofile> <file.c>)
#
#  The output executable is place in the ./bin directory. It is created as needed.
#
#  An option to log gcc output is provided through '-log'. All remaining arguments
#  are taken to be additional cflags. If '-log' is provided, then the compile log
#  is place in ./log/<ofile>_gcc.log. The ./log dir is created as needed. Example:
#
#   $ ./bgc.sh <ofile> <file.c> -Wextra -log -Wunused -Werror
#
#     gcc -Wall -Wextra -Wunused -Werror -o bin/<ofile> <file.c> 1>&2 \
#     | tee -a log/<ofile>_gcc.log
#
#  If the file './bldflags' exists in the present directory, its contents are
#  read into the script as additional flags to pass to gcc. It is intended to
#  provide a simple way of specifying additional libraries common to the source
#  files to be built. (e.g. -lssl -lcrypto)
#
#  an alias g='./bgc.sh' further reduces typing (pick your favorite letter)
#
#  you can create a 'bldflags' file in the present working directory that
#  hold additional directives for gcc. For using custom libraries of your
#  own making, the following bldflags file will allow automatic header
#  inclusion and library inclusion via rpath from non-std directories:
#
#  -I/home/david/inc -L/home/david/lib -Wl,-rpath=/home/david/lib
#

function help {
  local ecode=${2:-0}

  [[ -n $1 ]] && printf "\n $1\n" >&2

cat >&2 << helpMessage

  Usage: ${0##*/} <ofile> <file.c> [ <cflags> ... --log [ \$(<./bldflags)]]

    ${0##*/} calls 'gcc -Wall -o <ofile> <file.c> <cflags> <\$(<./bldflags)>'
    If the file './bldflags' exists in the present directory, its contents are
    read into the script as additional flags to pass to gcc. It is intended to
    provide a simple way of specifying additional libraries common to the source
    files to be built. (e.g. -lssl -lcrypto).

    If the -log option is given, then the compile string and compiler ouput are
    written to a long file in ./log/<ofile>_gcc.log

  Options:

    -h  |  --help  program help (this file)
    -l  |  --log   write compile string and compiler ouput to ./log/<ofile>_gcc.log

helpMessage

  exit $ecode
}

function usage {
  local ecode=${2:-0}

  [[ -n $1 ]] && printf "\n $1\n" >&2

  printf "\n  Usage: %s <ofile> <file.c> [ <cflags> ... --log [ \$(<./bldflags)]]\n\n" "${0##*/}"

  exit $ecode
}

logfn="log/${1}_gcc.log"
tstamp="$(date '+%b %e %T')"
mklog=-1
numargs="${#@}"
debug=0
opt=""
cflags="-Wall -Wextra -pedantic -finline-functions -std=gnu11"

## get gcc version for -0fast options check
gccv=$(gcc --version |
       head -n1 |
       sed -e 's/^.*\([0-9][.][0-9][.][0-9]\).*$/\1/')
gccvn=${gccv//./}   ## convert version to number (e.g. 5.2.0 -> 520)

## test for help and log flags and parse remaining args as cflags
for i in $*; do
    test "$i" = "-h" || test "$i" = "--help" && help
    test "$i" = "-l" || test "$i" = "--log" && mklog=0
    test "$i" = "-g" && debug=1
    test "${i:0:2}" = "-O" && opt="$i"
done

test -n "$1" && test -n "$2" || usage "error: insufficient input" 1
test "${2//*\.}" = "c" || usage "error: invalid input, '$2' is not a C-file (.c)" 1
test -f "$2" || usage "error: file not found '$2'" 1
if test -z "$opt" ; then
    if test $gccvn -ge 460 ; then   ## check gcc version >= 4.6.0 for -0fast options
        test "$debug" -eq 1 || cflags="${cflags} -Ofast"
    else
        test "$debug" -eq 1 || cflags="${cflags} -O3"
    fi
fi

if test "$mklog" -eq -1; then
    test "$numargs" -gt 2 && cflags="${cflags} ${@:3}"
elif test "$numargs" -ge 3; then
    for i in "${@:3}"; do
        test "$i" = "-l" && continue
        test "$i" = "--log" && continue
        cflags="${cflags} $i"
    done
fi

## if "./bldflags" exist, read contents into ldflags
test -f "./bldflags" && ldflags="$(<./bldflags)"

## test for file bin, move if exists, create bin dir
test -f "bin" && mv "bin" "bin.sav"
mkdir -p "bin"

## provide $cflags for any additional options or flags desired
#  $cflags must be unquoted to prevent resolving to "" when empty
#  and should remain uninitialized unless and until set
if test "$mklog" -eq 0; then

    ## test for file log, move if exists, create log dir
    test -f "log" && mv "log" "log.sav"
    mkdir -p "log"

    printf -- "--\n  gcc $cflags -o bin/%s %s $ldflags | tee -a %s\n--\n" "$1" "$2" "$logfn"
    printf "  %s  gcc %s -o bin/%s %s %s\n" "$tstamp" "$cflags" "$1" "$2" "$ldflags" | tee -a "$logfn"
    gcc $cflags -o "bin/$1" "$2" $ldflags 2>&1 | tee -a "$logfn"
else
    printf -- "--\n  gcc $cflags -o bin/%s %s $ldflags\n--\n" "$1" "$2"
    gcc $cflags -o "bin/$1" "$2" $ldflags
fi

exit 0