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bash/pangram/README.md

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+# Pangram
+
+Determine if a sentence is a pangram. A pangram (Greek: παν γράμμα, pan gramma,
+"every letter") is a sentence using every letter of the alphabet at least once.
+The best known English pangram is:
+> The quick brown fox jumps over the lazy dog.
+
+The alphabet used consists of ASCII letters `a` to `z`, inclusive, and is case
+insensitive. Input will not contain non-ASCII symbols.
+
+
+Run the tests with:
+
+```bash
+bats pangram_test.sh
+```
+
+After the first test(s) pass, continue by commenting out or removing the
+`[[ $BATS_RUN_SKIPPED == true ]] || skip` 
+annotations prepending other tests.
+
+To run all tests, including the ones with `skip` annotations, run:
+
+```bash
+BATS_RUN_SKIPPED=true bats pangram_test.sh
+```
+
+## Source
+
+Wikipedia [https://en.wikipedia.org/wiki/Pangram](https://en.wikipedia.org/wiki/Pangram)
+
+
+## External utilities
+`Bash` is a language to write "scripts" -- programs that can call
+external tools, such as
+[`sed`](https://www.gnu.org/software/sed/),
+[`awk`](https://www.gnu.org/software/gawk/),
+[`date`](https://www.gnu.org/software/coreutils/manual/html_node/date-invocation.html)
+and even programs written in other programming languages, 
+like [`Python`](https://www.python.org/).
+This track does not restrict the usage of these utilities, and as long
+as your solution is portable between systems and does not require
+installation of third party applications, feel free to use them to solve
+the exercise.
+
+For an extra challenge, if you would like to have a better understanding
+of the language, try to re-implement the solution in pure `Bash`,
+without using any external tools. Note that there are some types of
+problems that bash cannot solve, such as performing floating point
+arithmetic and manipulating dates: for those, you must call out to an
+external tool.
+
+## Submitting Incomplete Solutions
+It's possible to submit an incomplete solution so you can see how others
+have completed the exercise.

bash/pangram/pangram.sh

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+#!/usr/bin/env bash
+
+# set to mask to enable logs. 0: none, 255: all
+# (( debug=2#00001111 ))
+(( debug=2#00000000 ))
+
+# $1: log level (mask), then strings to display.
+debug () {
+    (( debug & "$1" )) && shift && echo "${@}" >&2
+}
+
+usage () {
+    echo "usage: ./pangram.sh <string> [...]" >&2
+    exit 1
+}
+
+# basic args checks: at least 1 arg
+(( $# )) || usage
+
+# We will accept mutiple args here: "a" "b" is equivalent to "ab".
+# get args in one string, change it to lower case.
+IFS=""                                                      # not really needed
+string="${*,,}"
+debug 1 "string=$string"
+
+# empty string
+if (( ! ${#string} )); then
+    debug 2 "empty string"
+    result=false
+else
+    result=true
+
+    # loop on all characters, from a to z. We need to check each one.
+    for c in {a..z} ; do
+        [[ ! ${string} =~ "$c" ]] && result=false && break
+    done
+fi
+
+echo "$result"
+exit 0
+
+# emacs/vim settings.
+# Local Variables:
+# sh-basic-offset: 4
+# indent-tabs-mode: nil
+# comment-column: 60
+# fill-column: 80
+# End:
+# vim: set tabstop=4 expandtab: