Add apf func (argument prepend [from] file)

1 files changed, 100 insertions, 0 deletions

diff --git a/bash/bashrc.d/apf.bash b/bash/bashrc.d/apf.bash
new file mode 100644
index 00000000..af759577
--- /dev/null
+++ b/bash/bashrc.d/apf.bash
@@ -0,0 +1,100 @@
+#
+# apf -- arg-prepend-file -- Prepend null-delimited arguments read from a file
+# to a command's arguments before running it. This is intended as a way of
+# implementing *rc files for interactive Bash calls to programs that don't
+# support such files, without having to use broken environment variables (e.g.
+# GREP_OPTIONS); this enables you to, for example, use arguments with shell
+# metacharacters and spaces in them that you do not want expanded.
+#
+# For example, given this simple program in our $PATH, printargs:
+#
+#   $ cat ~/.local/bin/printargs
+#   #!/bin/sh
+#   printf '%s\n' "$@"
+#
+# Which just prints its arguments:
+#
+#   $ printargs a b c
+#   a
+#   b
+#   c
+#
+# We could do this:
+#
+#   $ printf '%s\0' -f --flag --option '? foo bar *' > "$HOME"/.printargsrc
+#
+#   $ apf "$HOME"/.printargsrc printargs a b c
+#   -f
+#   --flag
+#   --option
+#   ? foo bar *
+#   a
+#   b
+#   c
+#
+# We could then make a permanent wrapper function with:
+#
+#   $ printargs() { apf "$HOME"/.printargsrc printargs "$@" ; }
+#
+#   $ printargs a b c
+#   -f
+#   --flag
+#   --option
+#   ? foo bar *
+#   a
+#   b
+#   c
+#
+#   $ printf '%s\n' !-2:q >> "$HOME"/.bashrc
+#
+# This means you can edit the options in the *rc file and don't have to
+# redefine a wrapper function.
+#
+# If you actually want those options to *always* be added, regardless of
+# whether you're in an interactive shell, you really should make an actual
+# wrapper script.
+#
+apf() {
+
+    # Require at least two arguments, give usage otherwise
+    if (($# < 2)) ; then
+        printf 'bash: %s: usage: %s ARGFILE COMMAND [ARGS...]\n' \
+            "$FUNCNAME" "$FUNCNAME" >&2
+        return 2
+    fi
+
+    # First argument is the file containing the null-delimited arguments
+    local argfile=$1
+    shift
+
+    # Check the arguments file makes sense
+    if [[ ! -e $argfile ]] ; then
+        printf 'bash: %s: %s: No such file or directory\n' \
+            "$FUNCNAME" "$argfile"
+        return 1
+    elif [[ -d $argfile ]] ; then
+        printf 'bash: %s: %s: Is a directory\n' \
+            "$FUNCNAME" "$argfile"
+        return 1
+    elif [[ ! -r $argfile ]] ; then
+        printf 'bash: %s: %s: Permission denied\n' \
+            "$FUNCNAME" "$argfile"
+        return 1
+    fi
+
+    # Read all the null-delimited arguments from the file
+    local -a args
+    local arg
+    while read -d '' -r arg ; do
+        args=("${args[@]}" "$arg")
+    done < "$argfile"
+
+    # Next argument is the command to run
+    local cmd=$1
+    shift
+
+    # Run the command with the retrieved arguments first, then the rest of the
+    # command line as passed to the function
+    command "$cmd" "${args[@]}" "$@"
+}
+