Programming Escape Characters

This page examines the nuances of escape characters used in C and Java program coding.

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The Escape characters

Escape Sequence	Description	VB Constant	ASCII	Hex	Unicode
\t	(Horizontal) Tab	vbTab	011	09	\u0009
\v	Vertical Tab	vbVerticalTab
\n	New Line Feed (LF)	vbLf vbNewLine	012	0A	\u000a
\r	Carriage Return (CR)	vbCr	015	0D	\u000d
\f	Form Feed	vbFormFeed	014	0C	\u000c
\b	Backspace	vbBack	010	08	\u0008
\\	Back slash (solidus)	-	092	5C	\u005c
\'	Single quote (grave accent)	-	060	27	\u0027
\"	Double quote	-	148	22	\u0022
\0	null (C string terminator)	vbNullChar	-		\u0000
\c	continuation (UNIX)
	null (Empty) string	vbNullString	-		-
	infinity(INF)	-	236		\u221E \u8734
\a	New line break for CSS2 content

PHP programs also need escaped dollars signs (which precede variable names), braces, and brackets (which have special meaning in PHP):
\$ \{ \} \[ \]

In DOS batch files, the character like the backslash in Linux is the carrot, which tells the command interpreter to see the next character as a conventional character. An example usage is this:

@echo off
set username=josh
echo ^<%username%@mail.com^> >> emaillist.txt

End of Line characters

Each platform has a different convention is for terminating lines:
• On Unix, an ASCII newline (\n) LF (linefeed) character ends each line.
• On Windows, an ASCII sequence CR LF (\r\n) (return followed by linefeed) ends each line.
• On Macintosh, an ASCII CR (\r) (carriage return) character ends each line.

Within UNIX, convert DOS newlines (CR/LF) to Unix format with this regular expression command:

sed 's/.$//' file # assumes that all lines end with CR/LF

Within DOS, convert Unix newlines (LF) to DOS \r\n format with one of these two regular expression commands:

sed 's/$//' file # method 1
sed -n p file # method 2

Use this standard utility:

dos2unix fromfile1 tofile

Flip-xp.exe is a FREE command-line utility you can download to your Windows\System32 folder to display (-t) or convert ASCII files to Unix (-u) or to Windows (-d) or to Macintosh (-m).

Removing Trailing Characters

Starting with Python 2.2, to remove all occurances of any line terminator from the end of the string S without removing other trailing whitespace:

S.rstrip("\r\n")

This is similar to Perl's chomp().

Setting Escape characters

Oracle SQLPLUS recognizes the & ampersand character as a substitution character for data input.

So to store a string such as "Johnson & Son" into an Oracle table, use an escape character, as in 'Johnson \& Son' (with the \&).

But first turn on escape character processing:

SQL> set escape \

Use in UNIX Shells

UNIX Korn shells use the \c escape character to signal continuation (no automatic line break):
echo "Enter the path to the data file: \c"