feat(user/combine_pdfs.sh):Add script to combine PDFs with pdftk

diff --git a/user/combine_pdfs.sh b/user/combine_pdfs.sh
new file mode 100755 (executable)
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+++ b/user/combine_pdfs.sh
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+#!/usr/bin/env bash
+# Desc: Combines PDF files into a single PDF file
+# Depends: pdftk 2.02-5 ( https://www.pdflabs.com/tools/pdftk-the-pdf-toolkit/ )
+# Version 0.0.1
+
+yell() { echo "$0: $*" >&2; } # print script path and all args to stderr
+die() { yell "$*"; exit 111; } # same as yell() but non-zero exit status
+must() { "$@" || die "cannot $*"; } # runs args as command, reports args if command fails
+showUsage() {
+    # Desc: Display script usage information
+    # Usage: showUsage
+    # Version 0.0.2
+    # Input: none
+    # Output: stdout
+    # Depends: GNU-coreutils 8.30 (cat)
+    cat <<'EOF'
+    USAGE:
+        combine_pdfs.sh [FILE output] [FILES input...]
+
+    EXAMPLE:
+      combine_pdfs.sh output.pdf input1.pdf input2.pdf
+      combine_pdfs.sh output.pdf input*.pdf
+EOF
+} # Display information on how to use this script.
+checkDepends() {
+    if ! command -v pdftk 1>/dev/random 2>&1; then
+        showUsage;
+        die "FATAL:Missing pdftk."; fi;
+}; # Check dependencies
+checkArgs() {
+    local narg;
+    
+    # Check arguments
+    narg=0;
+    for arg in "$@"; do
+        #yell "DEBUG:Checking argument:$arg";
+        if [[ $narg -le 0 ]]; then
+            if [[ ! -f "$arg" ]]; then
+                ((narg++)); continue;
+            else
+                ## Get permission to overwrite existing output file
+                yell "WARNING:Overwrite output file \"$arg\"? (y/n)";
+                read -r prompt;
+                case "$prompt" in
+                    "y" | "yes" | "Yes" | "YES" )
+                        ;;
+                    "n" | "no" | "No" | "NO" )
+                        showUsage; die "FATAL:Aborted.";
+                        ;;
+                    *)
+                        showUsage; die "FATAL:Invalid response.";
+                        ;;
+                esac;
+            fi;
+        fi; # handle first arg
+        
+        if [[ ! -f "$arg" ]]; then
+            showUsage; die "FATAL:File does not exist:$arg"; fi;
+        ((narg++));
+    done;
+
+    return 0;
+};
+combinePDFs() {
+    # Desc: Combines PDFs and writes to output PDF file
+    # Depends: pdftk 2.02-5
+    local cmd path_fo;
+    local -a paths_fi;
+
+    # Save output file path
+    path_fo="$1";
+    
+    # Form array of input file paths
+    paths_fi=("$@");
+    unset 'paths_fi[0]'; # discard first path which is output file
+
+    # Form command array
+    cmd+=("pdftk"); # executable
+    cmd+=("${paths_fi[@]}"); # input file paths
+    cmd+=("cat" "output");
+    cmd+=("$path_fo");
+    #yell "DEBUG:cmd:$(declare -p cmd)";
+    #yell "DEBUG:cmd:${cmd[*]}";
+
+    # Execute command array
+    "${cmd[@]}";
+}; # Combines PDFs and writes to output PDF file
+main() {
+    #yell "DEBUG:$(args=("$@"); declare -p args)";
+    checkDepends;
+    checkArgs "$@";
+    combinePDFs "$@";
+    exit 0;
+}; # main program
+
+main "$@";
+
+# Author: Steven Baltakatei Sandoval
+# License: GPLv3+
+
+# # Copyright notices
+
+# pdftk port to java 3.2.2 a Handy Tool for Manipulating PDF Documents
+# Copyright (c) 2017-2018 Marc Vinyals - https://gitlab.com/pdftk-java/pdftk
+# Copyright (c) 2003-2013 Steward and Lee, LLC.
+# pdftk includes a modified version of the iText library.
+# Copyright (c) 1999-2009 Bruno Lowagie, Paulo Soares, et al.
+# This is free software; see the source code for copying conditions. There is
+# NO warranty, not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+