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Full Discussion: Changing PS1
Top Forums Shell Programming and Scripting Changing PS1 Post 302733521 by alister on Tuesday 20th of November 2012 03:36:03 PM
Old 11-20-2012
Quote:
Originally Posted by Corona688
Insert a 'true' after it to force $? back to 0.

Unfortunately this will change the value of $? if you were wanting to depend on it later...
Command substitution never affects the value of $?, and that's the only way to execute anything from within the prompt string.

I don't think it's possible to cause the expansion of PS1 to alter the value of $?. If you (or anyone else) knows of a way, I'd appreciate knowing about it.


Quote:
Originally Posted by kristinu
Code:
    PS1="\[\033[0;37m\]\342\224\214\342\224\200 ...

My problem is that if I just press enter, I do not want to have the ✗ printed.
Since you neglected to be specific, I'm assuming this is for bash.

It seems like what you need is a way to detect when no command was entered at the prompt. Bash makes available the command number through the escape sequence \#. This value (at least with the version with which I tested) is not incremented for a null command. Testing its current value against its value at the time of the previous prompt's expansion should be sufficient to make a determination.

Since any variables set in the command substition subshell are lost when the shell exists, and since environmental changes cannot propagate from a child to a parent, the only way to store the command number for future inspection is to write it to a file.

The following example is intended only as a proof of concept. Aside from the minor inefficiency of reading a file for each prompt, it doesn't support simultaneously interactive shells (although it could, with some work and help from $$). The prompt consists simply of the exit status followed by a colon and a space. If no command was entered, regardless of the value of $?, a 0 is printed (analgous to not printing the X in your original problem statement):
Code:
PS1='$(ES=$?; LC=$(< ~/.lastcmd); if [ \# -eq ${LC:-0} ]; then echo 0; else echo $ES; fi; echo \# > ~/.lastcmd): '

Regards,
Alister
 

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asadmin-multimode(1AS)													    asadmin-multimode(1AS)

NAME
asadmin-multimode, multimode - allows you to execute multiple commands while preserving environment settings and remaining in the asadmin utility SYNOPSIS
multimode [--file filename] [--printprompt=true] [--encoding encode] [--terse=false] [--echo=false] Use multimode to process the asadmin commands. The command-line interface will prompt you for a command, execute that command, display the results of the command, and then prompt you for the next command. Additionally, all the asadmin option names set in this mode are used for all the subsequent commands. You can set your environment and run commands until you exit multimode by typing "exit" or "quit." You can also provide commands by passing a previously prepared list of commands from a file or standard input (pipe). You can invoke multimode from within a multimode session; once you exit the second multimode environment, you return to your original multimode environment. This command is supported in local mode only. --file reads the commands as defined in the file. --printprompt allows the printing of asadmin prompt after each command is executed. Set this option to false when the commands are piped or redirected from the standard input or file. By default the option is set to true. --encoding specifies the locale for the file to be decoded. --terse indicates that any output data must be very concise, typically avoiding human-friendly sentences and favoring well- formatted data for consumption by a script. Default is false. --echo setting to true will echo the command line statement on to the standard output. Default is false. Example 1: Using multimode to execute multiple commands example% asadmin multimode --file commands_file.txt Where: example% is the system prompt. The multimode settings are executed from the commands_file.txt file. EXIT STATUS
0 command executed successfully 1 error in executing the command asadmin-export(1AS), asadmin-unset(1AS) J2EE 1.4 SDK March 2004 asadmin-multimode(1AS)
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