10-15-2012
Shell quoting rules for other languages programmers
I've seen so many times that programmers were confused about shell quoting and white spaces interpretation, that I decided to investigate that problem deeper. And my conclusion is that quoting in shells is
very different from other programming languages. Programmers who have bigger experience in C/Python/Java/PHP than in Shell should remember about two
unintuitive rules:
- everything in shell is a string, and one need to quote everything properly. Also when reading variables: "$X", not only storing X="hi there"
- shell will parse lines of code just one time, leaving unresolved nested variables and commands. In this case programmer need to explicitly use "eval" function.
I've written short article about this if anyone will be more curious you can find it under "white shell cofoh"
This User Gave Thanks to wyderkat For This Post:
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LEARN ABOUT DEBIAN
string::parity
Parity(3) User Contributed Perl Documentation Parity(3)
NAME
String::Parity, setEvenParity, setOddParity, setSpaceParity, setMarkParity, isEvenParity, isOddParity isSpaceParity, isMarkParity, Even-
Bytes, OddBytes, SpaceBytes, MarkBytes, showParity, showMarkSpace - Parity (odd/even/mark/space) handling functions
SYNOPSIS
use String::Parity;
use String::Parity qw(:DEFAULT /show/);
DESCRIPTION
setEvenParity LIST
Copies the elements of LIST to a new list and converts the new elements to strings of bytes with even parity. In array context
returns the new list. In scalar context joins the elements of the new list into a single string and returns the string.
setOddParity LIST
Like setEvenParity function, but converts to strings with odd parity.
setSpaceParity LIST
Like setEvenParity function, but converts to strings with space (High bit cleared) parity.
setMarkParity LIST
Like setEvenParity function, but converts to strings with mark (High bit set) parity.
EvenBytes LIST
Returns the number of even parity bytes in the elements of LIST.
OddBytes LIST
Returns the number of odd parity bytes in the elements of LIST.
SpaceBytes LIST
Returns the number of space parity bytes in the elements of LIST.
MarkBytes LIST
Returns the number of mark parity bytes in the elements of LIST.
isEvenParity LIST
Returns TRUE if the LIST contains no byte with odd parity, FALSE otherwise.
isOddParity LIST
Returns TRUE if the LIST contains no byte with even parity, FALSE otherwise.
isSpaceParity LIST
Returns TRUE if the LIST contains no byte with mark parity, FALSE otherwise.
isMarkParity LIST
Returns TRUE if the LIST contains no byte with space parity, FALSE otherwise.
showParity LIST
Like setEvenParity function, but converts bytes with even parity to 'e' and other bytes to 'o'. The function showParity must be
imported by a specialised import list.
showMarkSpace LIST
Like setEvenParity function, but converts bytes with space parity to 's' and other bytes to 'm'. The function showMarkSpace must
be imported by a specialised import list.
NOTES
Don't use this module unless you have to communicate with some old device or protocol. Please make your application 8 bit clean and use the
internationally standardised ISO-8859-1 character set.
AUTHOR
Winfried Koenig <win@in.rhein-main.de>
SEE ALSO
perl(1), Exporter(1)
perl v5.8.0 1996-12-10 Parity(3)