8.15.1 Special Characters

The C shell has several more special characters than the Bourne shell:

! { } ~

8.15.2 How Quoting Works

Table 8.2 summarizes the rules; you might want to look back at it while you read the examples.

The major differences between C and Bourne shell quoting are:

• The exclamation point (!) character can only be quoted with a backslash. That's true inside and outside single or double quotes. So, you can use history substitution (11.7) inside quotes. For example:

  % grep intelligent engineering file*.txt
  grep: engineering: No such file or directory
  % grep '!:1-2' !:3
  grep 'intelligent engineering' file*.txt
      ...

• In the Bourne shell, inside double quotes, a backslash (\) stops variable and command substitution (it turns off the special meaning of $ and `).

  In the C shell, you can't disable the special meaning of $ or ` inside double quotes. You'll need a mixture of single and double quotes. For example, searching for the string use the `-c' switch takes some work:

  % fgrep "use the \`-c' switch" *.txt
  Unmatched \`.
  % fgrep 'use the \`-c\' switch' *.txt
  Unmatched '.
  % fgrep "use the "'`-c'"' switch" *.txt
  hints.txt:Be sure to use the `-c' switch.

  Article 10.8 shows an amazing pair of aliases that automate complicated quoting problems like this.

• In the Bourne shell, single and double quotes include newline characters. Once you open a single or double quote, you can type multiple lines before the closing quote.

  In the C shell, if the quotes on a command line don't match, the shell will print an error. To quote more than one line, type a backslash at the end of each line. Inside single or double quotes, the backslash-newline becomes a newline. Unquoted, backslash-newline is an argument separator:

  % echo "one\
  two" three\
  four
  one
  two three four