Improve wording & code readability of xargs

I've also un-squished flags & their arguments to avoid confusion.

sheets/xargs

@@ -1,26 +1,32 @@
-# Find all file names ending with .pdf and remove them
+# xargs
+# Build and execute command lines from standard input
+
+# Find all file names ending with .pdf, then remove them.
 find -name \*.pdf | xargs rm
-# The above, however, is preferable written without xargs:
+# The above, however, is better-written without xargs:
 find -name \*.pdf -exec rm {} \+
-# Or, for find's own functionality, it's best as:
+# Although it's best to use find's own functionality, in this situation.
 find -name \*.pdf -delete
 
-# Find all file name ending with .pdf and remove them
+# Find all file names ending with '.pdf' and remove them. This approach also
-# (bulletproof version: handles filenames with \n and skips *.pdf directories)
+# handles filenames with '\n' and skips '*.pdf' directories. The xargs(1) flag
-# -r = --no-run-if-empty
+# `-r` is equivalent to `--no-run-if-empty`, and the use of `-n` will in this
-# -n10 = group by 10 files
+# case group execution by 10 files.
-find -name \*.pdf -type f -print0 | xargs -0rn10 rm
+find -name \*.pdf -type f -print0 | xargs -0 -r -n 10 rm
 
-# If file name contains spaces you should use this instead
+# If file names may contains spaces, you can use the xargs(1) flag `-I` and its
-find -name \*.pdf | xargs -I{} rm -rf '{}'
+# proceeding argument to specify the filename placeholder, as in find(1)'s use
+# of `{}` in `-exec`. Although find(1)'s `{}` needs not be cuddled by quotes, -
+# xargs(1) does.
+find -name \*.pdf | xargs -I {} rm -r '{}'
 
-# Will show every .pdf like:
+# Print a list of files in the format of `*FILE=`. The use of xargs(1) flag
-#    &toto.pdf=
+# `-n` here with its argument of `1` means to process the files one-by-one.
-#    &titi.pdf=
+find -name \*.pdf | xargs -I {} -n 1 echo '&{}='
-# -n1 => One file by one file. ( -n2 => 2 files by 2 files )
+# The above is, however, much faster, more efficient, and easier without xargs.
-find -name \*.pdf | xargs -I{} -n1 echo '&{}='
+find -name \*.pdf -printf '&%f=\n'
-# The above is, however, much faster and easier without xargs:
-find -name \*.pdf -printf "%p\n"
 
-# Group words by three in a string
+# Group words by three in a string.
-seq 1 10 | xargs -n3
+seq 1 10 | xargs -n 3
+# Alternatively, and more efficiently, use Bash brace expansion, if available.
+printf '%d ' {1..10} | xargs -n 3