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Full Discussion: Environment variables
Top Forums UNIX for Dummies Questions & Answers Environment variables Post 302464274 by DGPickett on Tuesday 19th of October 2010 04:07:29 PM
Old 10-19-2010
I seem to recall csh was semi-case-insensitive, another reason to stay away.

'PATH' is hard coded into exec(), the library path variable whatever it is on the brand in the synamic linker, MANPATH into man, and '$PWD' changes no matter how you change the working directory, so the environment has many frozen variables. I checked my local CScope web utility. Lots of include files mention PATH, but none has "PATH" -- maybe in the kernel C?

Code:
                                                                             /usr/include/limits.h  <unknown>     71  #  define _POSIX_PATH_MAX	255 	/* The number of bytes in a pathname */
                                                                             /usr/include/limits.h  <unknown>    284  #    define PATH_MAX   	1023	/* max number of characters in a pathname (not
                                                                          /usr/include/sys/param.h  <unknown>    388  * MAXPATHLEN defines the longest permissable path length
                                                                          /usr/include/sys/param.h  <unknown>    398  #define MAXPATHLEN	1024
                                                                 /usr/include/.unsupp/sys/_errno.h  <unknown>     22  #  define EPATHREMOTE		133	/* Pathname is remote */
                                                                         /usr/include/sys/unistd.h  <unknown>    712  #  define _PC_PATH_MAX		4  /* PATH_MAX: Max # of bytes in a pathname */
                                                                         /usr/include/sys/unistd.h  <unknown>    800  #  define _CS_PATH	200	/* Search path that finds all POSIX.2 utils */
                                                                         /usr/include/sys/unistd.h  <unknown>    873  #  define GF_PATH	"/etc/group"	/* Path name of the "group" file */
                                                                         /usr/include/sys/unistd.h  <unknown>    874  #  define PF_PATH	"/etc/passwd"	/* Path name of the "passwd" file */
                                                                         /usr/include/sys/unistd.h  <unknown>    875  #  define IN_PATH	"/usr/include"	/* Path name for <...> files */
                                                                         /usr/include/sys/unistd.h  <unknown>    880  #  define CS_PATH	  \
                                                                         /usr/include/sys/ptrace.h  <unknown>     79  #define	PT_GET_PROCESS_PATHNAME	23 /* Get Pathname for exec'd file */
                                                                         /usr/include/sys/ptrace.h  <unknown>     81  #define IS_PTRACE_REQ(i)   ((i) >= PT_SETTRC && (i) <= PT_GET_PROCESS_PATHNAME)
                                                                   /usr/include/sys/scall_define.h  <unknown>    323  #define	SYS_PATHCONF	230
                                                                   /usr/include/sys/scall_define.h  <unknown>    325  #define	SYS_FPATHCONF	231
                                                                   /usr/include/sys/scall_define.h  <unknown>    751  #define	SYS_SENDPATH	480
                                                                   /usr/include/sys/scall_define.h  <unknown>    755  #define	SYS_SENDPATH64	482
                                                                   /usr/include/sys/scall_define.h  <unknown>    761  #define	SYS_MODPATH	485
                                                                      /usr/include/sys/semglobal.h  <unknown>    231  * DLM_MPATH_LOCK_ORDER		mod_mpath_lock: rw-sleep
                                                                      /usr/include/sys/semglobal.h  <unknown>    241  #define DLM_MPATH_LOCK_ORDER	DLM_TOP_LOCK_ORDER - 20

 

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cd(1)							      General Commands Manual							     cd(1)

NAME
cd - Changes the current working directory SYNOPSIS
cd [directory] Note The C shell has a built-in version of the cd command. If you are using the C shell, and want to guarantee that you are using the command described here, you must specify the full path /usr/bin/cd. See the csh(1) reference page for a description of the built-in command. STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: cd: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
None OPERANDS
The pathname (either full or relative) to be used as the new working directory. If (hyphen) is specified as the directory, the cd command changes your current (working) directory to the directory name saved in the environment variable OLDPWD. DESCRIPTION
The cd command moves you from your present directory to another directory. You must have execute (search) permission in the specified directory. If you do not specify a directory, cd moves you to your login directory ($HOME in ksh and sh environments, or $home in csh environment). If the specified directory name is a full pathname, it becomes the current working directory. A full pathname begins with a / (slash) for the root directory, with a . (dot) for the current working directory, or with a .. (dot dot) for the parent directory. If the directory name is not a full pathname, cd searches for it relative to one of the paths specified by the $CDPATH shell variable (or $cdpath csh vari- able). This variable has the same syntax as, and similar semantics to, the $PATH shell variable (or $path csh variable). EXIT STATUS
The following exit values are returned: The directory was successfully changed. An error occurred. EXAMPLES
To change to your home directory, enter: cd To change to a new directory, enter: cd /usr/include This changes the current working directory to /usr/include. Now file pathnames that do not begin with / or ../ specify files located in /usr/include. To go down one level of the directory tree, enter: cd sys If the current working directory is /usr/include and if it contains a subdirectory named sys, then /usr/include/sys becomes the cur- rent working directory. To go up one level of the directory tree, enter: cd .. The special filename .. (dot dot) always refers to the directory immediately above the current working directory. ENVIRONMENT VARIABLES
The following environment variables affect the execution of cd: 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 cd command will search for directory relative to each directory named in the CDPATH variable, in the order listed. The new working directory will be set 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 will be treated as if it were an empty string. The name of the home directory, used when no directory operand is specified. Provides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization variables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, overrides the values of all the other internationalization variables. Determines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multibyte char- acters in arguments). Determines the locale for the format and contents of diagnostic messages written to standard error. Determines the location of message catalogues for the processing of LC_MESSAGES. A pathname of the previous working directory, used by the cd - form of the command. The cd command sets this variable to your current working directory before changing to a new current directory. A pathname of the current working directory, set by the cd command after it has changed to that directory. SEE ALSO
Commands: csh(1), ksh(1), pwd(1), Bourne shell sh(1b), POSIX shell sh(1p) Functions: chdir(2) Environment: environ(5) Standards: standards(5) cd(1)
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