implementing mkdir, chdir, mv, pwd inside a shell !

11-03-2009

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implementing mkdir, chdir, mv, pwd inside a shell !

1. The problem statement, all variables and given/known data:

need to implement mkdir, chdir, mv, pwd

given a shell.cpp directory.cpp and some other files

this shell missing these commands, and i need to implement them inside the shell

2. Relevant commands, code, scripts, algorithms:

shell included in this file:
http://avida.cs.wright.edu/courses/C...Winter.tar.bz2

3. The attempts at a solution (include all code and scripts):

the mkdir is not working from inside the shell. neither chdir , mv or pwd.

i successfuly implemented piping ,redirection, execution in the background in earlie assigment, but this assigment is not working out

4. School (University) and Course Number:

CEG433/CEG633 - Operating Systems

evantheking

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cd(1) User Commands cd(1) NAME
cd, chdir, pushd, popd, dirs - change working directory SYNOPSIS
/usr/bin/cd [directory] sh cd [argument] chdir [argument] csh cd [dir] chdir [dir] pushd [+n | dir] popd [+ n] dirs [-l] ksh cd [-L] [-P] [arg] cd old new DESCRIPTION
/usr/bin/cd The /usr/bin/cd utility changes the current directory in the context of the cd utility only. This is in contrast to the version built into the shell. /usr/bin/cd has no effect on the invoking process but can be used to determine whether or not a given directory can be set as the current directory. sh The Bourne shell built-in cd changes the current directory to argument. The shell parameter HOME is the default argument. The shell parame- ter CDPATH defines the search path for the directory containing argument. Alternative directory names are separated by a colon (:). The default path is <null> (specifying the current directory). The current directory is specified by a null path name, which can appear immedi- ately after the equal sign or between the colon delimiters anywhere else in the path list. If argument begins with `/', `.', or `.. ', the search path is not used. Otherwise, each directory in the path is searched for argument. cd must have execute (search) permission in argu- ment. Because a new process is created to execute each command, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the shell. (See pwd(1), sh(1), and chdir(2)). chdir is just another way to call cd. csh If dir is not specified, the C shell built-in cd uses the value of shell parameter HOME as the new working directory. If dir specifies a complete path starting with ` / ', ` . ', or ` .. ', dir becomes the new working directory. If neither case applies, cd tries to find the designated directory relative to one of the paths specified by the CDPATH shell variable. CDPATH has the same syntax as, and similar seman- tics to, the PATH shell variable. cd must have execute (search) permission in dir. Because a new process is created to execute each com- mand, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the C-shell. (See pwd(1), sh(1), and chdir(2)). chdir changes the shell's working directory to directory dir. If no argument is given, change to the home directory of the user. If dir is a relative pathname not found in the current directory, check for it in those directories listed in the cdpath variable. If dir is the name of a shell variable whose value starts with a /, change to the directory named by that value. pushd pushes a directory onto the directory stack. With no arguments, exchange the top two elements. +n Rotate the n'th entry to the top of the stack and cd to it. dir Push the current working directory onto the stack and change to dir. popd pops the directory stack and cd to the new top directory. The elements of the directory stack are numbered from 0 starting at the top. +n Discard the n'th entry in the stack. dirs prints the directory stack, most recent to the left; the first directory shown is the current directory. With the -l argument, produce an unabbreviated printout; use of the ~ notation is suppressed. ksh The Korn shell built-in cd command can be in either of two forms. In the first form it changes the current directory to arg. If arg is - the directory is changed to the previous directory. The shell variable HOME is the default arg. The environment variable PWD is set to the current directory. If the PWD is changed, the OLDPWD environment variable shall also be changed to the value of the old working directory, that is, the current working directory immediately prior to the call to change directory (cd). The shell variable CDPATH defines the search path for the directory containing arg. Alternative directory names are separated by a colon (:). The default path is null (specifying the current directory). The current directory is specified by a null path name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If arg begins with a ` / ', ` . ', or ` .. ', then the search path is not used. Other- wise, each directory in the path is searched for arg. If unsuccessful, cd attempts to change directories to the pathname formed by the con- catenation of the value of PWD, a slash character, and arg. -L Handles the operation dot-dot (..) logically. Symbolic link components are not resolved before dot-dot components are processed. -P Handles the operand dot-dot physically. Symbolic link components are resolved before dot-dot components are processed. If both -L and -P options are specified, the last option to be invoked is used and the other is ignored. If neither -L nor -P is specified, the operand is handled dot-dot logically. The second form of cd substitutes the string new for the string old in the current directory name, PWD and tries to change to this new directory. The cd command cannot be executed by rksh. Because a new process is created to execute each command, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the Korn shell. (See pwd(1), sh(1), and chdir(2)). OPERANDS
The following operands are supported: directory An absolute or relative pathname of the directory that becomes the new working directory. The interpretation of a relative pathname by cd depends on the CDPATH environment variable. OUTPUT
If a non-empty directory name from CDPATH is used, an absolute pathname of the new working directory is written to the standard output as follows: "%s ", <new directory> Otherwise, there is no output. ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of cd: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. CDPATH A colon-separated list of pathnames that refer to directories. If the directory operand does not begin with a slash ( / ) character, and the first component is not dot or dot-dot, cd searches for directory relative to each directory named in the CDPATH variable, in the order listed. The new working directory sets to the first matching directory found. An empty string in place of a directory pathname represents the current directory. If CDPATH is not set, it is treated as if it were an empty string. HOME The name of the home directory, used when no directory operand is specified. OLDPWD A pathname of the previous working directory, used by cd-. PWD A pathname of the current working directory, set by cd after it has changed to that directory. EXIT STATUS
The following exit values are returned by cd: 0 The directory was successfully changed. >0 An error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ SEE ALSO
csh(1), ksh(1), pwd(1), sh(1), chdir(2), attributes(5), environ(5), standards(5) SunOS 5.10 13 Jul 2004 cd(1)

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implementing mkdir, chdir, mv, pwd inside a shell !

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