06-15-2013
Note that the cd utility is a shell built-in; so the results of a test like this could vary widely from shell to shell.
Most shells will need to set the variable PWD when they start. Some shells will remember some number of directories they have seen in calls to cd and if they have seen a target direcotry path before, they can change the value of PWD (a side effect of calling cd) by looking at an in memory cache of previously visited directories. When you renamed subfol3 to subfol4, the shell's cache didn't contain an entry for subfol4 and had to make at least one system call to determine if subfol4 was a real directory or a symbolic link to a directory.
When you renamed subfol4 back to subfol3, the shell's cache could have contained an entry for subfol3, so it may have assumed that its cache was still valid.
If you look at the truss output (instead of just looking at the getcwd line in the output) you might be able to glean what is going on under the covers. You haven't said whether either of the subfol3 or subfol4 directories had been visited before the output you showed. My guess would be that you had visited subfol3 before, to get the results you showed, but without a lot more details this is purely speculation.
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CHSH(1) User Commands CHSH(1)
NAME
chsh - change login shell
SYNOPSIS
chsh [options] [LOGIN]
DESCRIPTION
The chsh command changes the user login shell. This determines the name of the user's initial login command. A normal user may only change
the login shell for her own account; the superuser may change the login shell for any account.
OPTIONS
The options which apply to the chsh command are:
-h, --help
Display help message and exit.
-R, --root CHROOT_DIR
Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.
-s, --shell SHELL
The name of the user's new login shell. Setting this field to blank causes the system to select the default login shell.
If the -s option is not selected, chsh operates in an interactive fashion, prompting the user with the current login shell. Enter the new
value to change the shell, or leave the line blank to use the current one. The current shell is displayed between a pair of [ ] marks.
NOTE
The only restriction placed on the login shell is that the command name must be listed in /etc/shells, unless the invoker is the superuser,
and then any value may be added. An account with a restricted login shell may not change her login shell. For this reason, placing /bin/rsh
in /etc/shells is discouraged since accidentally changing to a restricted shell would prevent the user from ever changing her login shell
back to its original value.
FILES
/etc/passwd
User account information.
/etc/shells
List of valid login shells.
/etc/login.defs
Shadow password suite configuration.
SEE ALSO
chfn(1), login.defs(5), passwd(5).
shadow-utils 4.5 01/25/2018 CHSH(1)