Escape
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The space character is an excellent example of a special character you may want to escape. If you want access a file that has a name with a space in it you need to '''escape''' this character, to ensure that it is not treated as a separator between file names, or between command line switches. | The space character is an excellent example of a special character you may want to escape. If you want access a file that has a name with a space in it you need to '''escape''' this character, to ensure that it is not treated as a separator between file names, or between command line switches. | ||
| − | If during a shell session you typed: | + | Let's say that you want to edit a file named '''my file.txt'''. If during a shell session you typed: |
# '''emacs my file.txt''' | # '''emacs my file.txt''' | ||
| − | emacs would try to open the files '''my''' and '''file.txt'''. | + | emacs would try to open the files '''my''' and '''file.txt''', which is not what you wanted. But if you escaped the space character: |
| − | + | ||
| − | + | ||
# '''emacs my\ file.txt''' | # '''emacs my\ file.txt''' | ||
| − | then emacs would | + | then emacs would open '''my file.txt''' as you intended. |
Conversely, '''n''' is an example of a normally non-special character which becomes special when escaped. If you want to [[echo]] carriage returns to standard output or to a file, you can't do it by pressing enter - that just executes the echo command (or begins another line in your script, if you're programming). What you need to do is use '''\n''' - because when you '''escape''' the n character, what you're telling the system is that you want a '''newline'''. | Conversely, '''n''' is an example of a normally non-special character which becomes special when escaped. If you want to [[echo]] carriage returns to standard output or to a file, you can't do it by pressing enter - that just executes the echo command (or begins another line in your script, if you're programming). What you need to do is use '''\n''' - because when you '''escape''' the n character, what you're telling the system is that you want a '''newline'''. | ||
[[Category:FreeBSD Terminology]] | [[Category:FreeBSD Terminology]] | ||
Revision as of 10:56, 28 January 2005
In unix-like systems, the escape character is not what you get when you press the escape key - it is the backslash (\), which is used to "escape" special characters when you don't want those special characters to perform their special functions - or, in some cases, to cause normally non-special characters to perform special functions.
The space character is an excellent example of a special character you may want to escape. If you want access a file that has a name with a space in it you need to escape this character, to ensure that it is not treated as a separator between file names, or between command line switches.
Let's say that you want to edit a file named my file.txt. If during a shell session you typed:
# emacs my file.txt
emacs would try to open the files my and file.txt, which is not what you wanted. But if you escaped the space character:
# emacs my\ file.txt
then emacs would open my file.txt as you intended.
Conversely, n is an example of a normally non-special character which becomes special when escaped. If you want to echo carriage returns to standard output or to a file, you can't do it by pressing enter - that just executes the echo command (or begins another line in your script, if you're programming). What you need to do is use \n - because when you escape the n character, what you're telling the system is that you want a newline.
