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Full Discussion: RFC - Korn shell prompt
Top Forums Shell Programming and Scripting RFC - Korn shell prompt Post 302905795 by gezley on Saturday 14th of June 2014 02:10:33 AM
Old 06-14-2014
RFC - Korn shell prompt

Hi,

I am learning shell scripting for the first time. I use AT&T Korn Shell, Version AJM 93u+ 2012-08-01, compiled from source on NetBSD.

So far I have managed to set up what I think is a useful and pleasing shell prompt, which can be seen in the image attached to this post.

The prompt is a multi-line prompt, as follows:

Line 1 (reverse video) shows the TERM variable, together with TTY, SHELL, and the date and time as it was when the prompt was updated.
(The print -f statement formats this line so that the text is right-aligned and the reverse-video bar takes up the whole width of the terminal, even if it is resized. It uses the COLUMNS variable to achieve this.)

Line 2 shows the host I am connected to (obscured for security).

Line 3 shows the job number and current working directory.

Line 4 shows the user name and the prompt itself.

I have just one problem: unless I symlink /bin/ksh93 to /bin/sh (the default shell on NetBSD) I get errors about "bad substitution". I am certain my prompt is causing this problem, but I still don't know enough to say what is wrong. Would somebody be so kind as to look at my PS1 and tell me where I am going wrong, and where I can improve it? I have learned quite a bit about if...then and case statements while learning how to do this prompt, but I am still unclear about brackets, single quotes and double quotes.

The following is the relevant part of my .kshrc file. I have split the PS1 lines for readability but they are all on one line in the file.

Code:
                                                                         
ttyhere=$(tty | sed -e "s:/dev/::")                                               
timenow=$(date +"%H:%M %Y%m%d")                                                   
currshell=$(print "$SHELL" | sed -e "s:/bin/::")                                  
                                                                                  
PS1='$(print -f "\n\E[1;7m%${COLUMNS}s\E[0m\n" "[$TERM] \
[$ttyhere] [$currshell] [Time at prompt: $timenow] "; \
print "[$(hostname)]"; \
print -n "[\E[1;36m!\E[0m]"; \
if [[ "${PWD#$HOME}" != "$PWD" ]] then; \
print "[\E[1;35m~${PWD#$HOME}\E[0m]"; \
else; print "[\E[1;35m$PWD\E[0m]"; fi; \
if [[ $(id -u) -ne 0 ]] then; \
print "[\E[1;36m$(id -un)\E[0m]$ "; \
else; print "[\E[1;35m$(id -un)\E[0m]# "; \
fi;)' ;;

RFC - Korn shell prompt-promptpng

Last edited by gezley; 06-14-2014 at 03:22 AM.. Reason: Formatting
 

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newgrp(1)							   User Commands							 newgrp(1)

NAME
newgrp - log in to a new group SYNOPSIS
Command /usr/bin/newgrp [-| -l] [group] sh Built-in newgrp [argument] ksh Built-in *newgrp [argument] ksh93 Built-in +newgrp [argument] DESCRIPTION
Command The newgrp command logs a user into a new group by changing a user's real and effective group ID. The user remains logged in and the cur- rent directory is unchanged. The execution of newgrp always replaces the current shell with a new shell, even if the command terminates with an error (unknown group). Any variable that is not exported is reset to null or its default value. Exported variables retain their values. System variables (such as PS1, PS2, PATH, MAIL, and HOME), are reset to default values unless they have been exported by the system or the user. For example, when a user has a primary prompt string (PS1) other than $ (default) and has not exported PS1, the user's PS1 is set to the default prompt string $, even if newgrp terminates with an error. Note that the shell command export (see sh(1) and set(1)) is the method to export variables so that they retain their assigned value when invoking new shells. With no operands and options, newgrp changes the user's group IDs (real and effective) back to the group specified in the user's password file entry. This is a way to exit the effect of an earlier newgrp command. A password is demanded if the group has a password and the user is not listed in /etc/group as being a member of that group. The only way to create a password for a group is to use passwd(1), then cut and paste the password from /etc/shadow to /etc/group. Group passwords are antiquated and not often used. sh Built-in Equivalent to exec newgrp argument where argument represents the options and/or operand of the newgrp command. ksh Built-in Equivalent to exec to/bin/newgrp argument where argument represents the options and/or operand of the newgrp command. On this man page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways: 1. Variable assignment lists preceding the command remain in effect when the command completes. 2. I/O redirections are processed after variable assignments. 3. Errors cause a script that contains them to abort. 4. Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file name genera- tion are not performed. ksh93 Built-in Equivalent to exec to/bin/newgrp argument where argument represents the options and/or operand of the newgrp command. On this man page, ksh93(1) commands that are preceded by one or two + (plus signs) are treated specially in the following ways: 1. Variable assignment lists preceding the command remain in effect when the command completes. 2. I/O redirections are processed after variable assignments. 3. Errors cause a script that contains them to abort. 4. They are not valid function names. 5. Words, following a command preceded by ++ that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This means that tilde substitution is performed after the = sign and field splitting and file name genera- tion are not performed. OPTIONS
The following option is supported: -l | - Change the environment to what would be expected if the user actually logged in again as a member of the new group. OPERANDS
The following operands are supported: group A group name from the group database or a non-negative numeric group ID. Specifies the group ID to which the real and effective group IDs is set. If group is a non-negative numeric string and exists in the group database as a group name (see getgr- nam(3C)), the numeric group ID associated with that group name is used as the group ID. argument sh and ksh only. Options and/or operand of the newgrp command. ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of newgrp: LANG, LC_ALL, LC_CTYPE, LC_MES- SAGES, and NLSPATH. EXIT STATUS
If newgrp succeeds in creating a new shell execution environment, whether or not the group identification was changed successfully, the exit status is the exit status of the shell. Otherwise, the following exit value is returned: >0 An error occurred. FILES
/etc/group System group file /etc/passwd System password file ATTRIBUTES
See attributes(5) for descriptions of the following attributes: /usr/bin/newgrp, ksh, sh +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ |Standard |See standards(5). | +-----------------------------+-----------------------------+ ksh93 +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |Interface Stability |Uncommitted | +-----------------------------+-----------------------------+ SEE ALSO
login(1), ksh(1), ksh93(1), set(1), sh(1), Intro(3), getgrnam(3C), group(4), passwd(4), attributes(5), environ(5), standards(5) SunOS 5.11 2 Nov 2007 newgrp(1)
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