Script for launching a subshell with modified PATH and LD_LIBRARY_PATH

subshell.sh

#!/bin/bash -e

ENVNAME='CMU 15-213'

START="$PWD"
cd "$(dirname "$0")"
BIN="$PWD/bin"
LIB="$PWD/lib"
mkdir -p "$BIN" "$LIB"
cd "$START"

_ensure_bin_ () {
    local des="$BIN/$1"
    local src="$2"
    printf '#!/bin/bash -e\n%s "$@"\n' "$src" >"$des" && chmod u+x "$des"
}

_ensure_lib_ () {
    local des="$LIB/$1"
    local src="$2"
    ln -sf "$src" "$des"
}

_we_roll_ () {(
    export PATH="$BIN:$PATH"
    export LD_LIBRARY_PATH="$LIB:$LD_LIBRARY_PATH"
    export PS1="[$ENVNAME] "'\u@\h:\w> '
    exec "$SHELL"
)}

# GCC

_ensure_bin_ gcc /usr/bin/gcc-11

# Clang/LLVM

_ensure_bin_ clang   /usr/bin/clang-14.0.6
_ensure_bin_ clang++ /usr/bin/clang++-14.0.6
_ensure_bin_ llvm    /usr/bin/llvm-14.0.6
_ensure_bin_ opt     /usr/bin/opt-14.0.6

_ensure_lib_ libLLVM-14.so.1 /usr/lib64/libLLVM.so.14

# ...And that's it!!
_we_roll_