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Full Discussion: Beginner Question about 2 specific functions
Top Forums Shell Programming and Scripting Beginner Question about 2 specific functions Post 302837115 by Skittlybop on Thursday 25th of July 2013 06:49:20 AM
Old 07-25-2013
Beginner Question about 2 specific functions
My professor has given me a couple of functions that I am to use to accomplish the task of replacing spaces in file and/or directory names with hyphens.

(i.e. A B/C D/E F and you want to rename that to A B/C D/E-F would be an example of changing the file and leaving the directories)

These are two of the functions I am to use:

Code:
pathname ()
    {
    # function provided for the student
    print -- "${1%/*}"
    }

basename ()
    {
    # function provided for the student
    print -- "${1##*/}"
    }

Basically they are to be used thusly:

1. FILE="A B/C D/E F"
2. BASENAME=`basename "$FILE"`
3. PATHNAME=`pathname "$FILE"`
4. NEWNAME=`echo $BASENAME | some sed command to change spaces to -'s '` # I will leave the sed command to you :-)
5. Now you have the pieces to do the rename à $FILE gets moved to "$PATHNAME/$NEWNAME"

I am wondering if someone can break down, in detail, what those two functions actually do. I'm not sure I understand how the regex and print fucntion work in them, and why are there two hyphens after print. Thanks in advance. Sorry for the long post.
Last edited by jim mcnamara; 07-25-2013 at 08:01 AM..
 

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LEARN ABOUT OSX

basename

BASENAME(3)						   BSD Library Functions Manual 					       BASENAME(3)

NAME

     basename -- extract the base portion of a pathname

SYNOPSIS

     #include <libgen.h>

     char *
     basename(char *path);

DESCRIPTION

     The basename() function returns the last component from the pathname pointed to by path, deleting any trailing '/' characters.  If path con-
     sists entirely of '/' characters, a pointer to the string "/" is returned.  If path is a null pointer or the empty string, a pointer to the
     string "." is returned.

RETURN VALUES

     On successful completion, basename() returns a pointer to the last component of path.

     If basename() fails, a null pointer is returned and the global variable errno is set to indicate the error.

ERRORS

     The following error codes may be set in errno:

     [ENAMETOOLONG]	The path component to be returned was larger than MAXPATHLEN.

WARNINGS

     The basename() function returns a pointer to internal static storage space that will be overwritten by subsequent calls.  The function may
     modify the string pointed to by path.

LEGACY SYNOPSIS

     #include <libgen.h>

     char *
     basename(const char *path);

     In legacy mode, path will not be changed.

SEE ALSO

     basename(1), dirname(1), dirname(3), compat(5)

STANDARDS

     The basename() function conforms to X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'').

HISTORY

     The basename() function first appeared in OpenBSD 2.2 and FreeBSD 4.2.

AUTHORS

     Todd C. Miller <Todd.Miller@courtesan.com>

BSD
								  August 17, 1997							       BSD
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