bash.tips-and-tricks.rme

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..                            BASH TIPS AND TRICKS                            ..
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~> THE FABLED TABLE OF CONTENTS
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Search the index number '>>>NNN<<<' to jump to it.

>>>001<<<   Oneliner
   Given multiple lines of text from a file or standard input, concatenate
   each line onto a single line and return to standard input. This assumes
   that each field is delimited with a space character. Another way of
   describing it is: replace all newline and tab characters with the space
   character, and remove duplicate space characters between fields.

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>>>002<<<   Standard File
   If standard input must be used and storing the contents to a temporary
   file is not feasible given available system resources, use a named pipe.
   Two shell processes must be used to spawn a reader and writer for the pipe,
   however, a single shell may be used if the reader process is backgrounded.

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>>>003<<<   Remove Non-Printable Chars
   Using tr, remove all non-printable characters from standard input and 
   output it to standard out.

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>>>004<<< 
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>>>010<<< 
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# ---------------------------------------------------------------------------- #
>>>001<<<   Oneliner
# ---------------------------------------------------------------------------- #
METHOD 1: using echo (file input). multiple files ok. if the input must be 
   from standard input, used a named pipe- see >>>002<<< .
$ echo $(<file1) [$(<file2) ...]

METHOD 2: using tr (standard input). Leaves trailing delimiter character.
$ grep PATTERN FILE | tr '\n' ' '
$ tr '\n' ' ' <FILE

METHOD 3: use awk (stdin).
$ grep PATTERN FILE | awk '{print}' ORS=' '
$ awk '{print}' ORS=' ' <FILE

# ---------------------------------------------------------------------------- #
>>>002<<<   Standard File
# ---------------------------------------------------------------------------- #
$ mkfifo mypipe1 [mypipe2 ...]
$ cat $(<mypipe1) [$(<mypipe2) ...] &        # reader process
$ echo file1 file2 file3 [...] > mypipe1     # example writer process
$ echo ...                                   # repeat for all named pipes
# each pipe must be written to before the reader will execute and unblock

# ---------------------------------------------------------------------------- #
>>>003<<<   Remove Non-Printable Chars
# ---------------------------------------------------------------------------- #
$ cat file1 [file2 ...] | tr -cd [:print:]
$ tr -cd [:print:] <FILE



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