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Top Forums Shell Programming and Scripting Question about special variables: "-" and "$_" Post 302405985 by kshji on Sunday 21st of March 2010 08:08:30 AM
Old 03-21-2010
If I open that page, it's include ex. this text:
_ (An underscore.) At shell startup, set to the absolute pathname used to invoke the shell or shell script being executed as passed in the environment or argument list. Subsequently, expands to the last argument to the previous command, after expansion. Also set to the full pathname used to invoke each command executed and placed in the environment exported to that command. When checking mail, this parameter holds the name of the mail file.

Those are variables (or parameters). If you like to get value of variable then add $ before variablename, like $_, $-, $!, $$, ...

Code:
ls -a -r -f
echo $_  # output -f

Give command line like: xxx -a -b
xxx:
Code:
echo $_
echo $0
echo $*
echo $$

Usually after you login $_ is maybe usable = your shell path.
You can save your shell path in the profile script
Code:
MYSHELL=$_
export MYSHELL

if you need it.
 

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jobs(1) 						      General Commands Manual							   jobs(1)

NAME
jobs - Displays status of jobs in the current session SYNOPSIS
jobs [-l | -p] job_id... [Tru64 UNIX] jobs [-n] job_id... Note The C shell has a built-in version of the jobs 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/jobs. 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: jobs: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
Provides more information about each job listed. This information includes the job number, current job, process group ID, state and the command that formed the job. Displays only the process IDs for the process group leaders of the selected jobs. [Tru64 UNIX] Displays jobs that have stopped or exited since last notified. By default, the jobs utility displays the status of all stopped jobs, running background jobs and all jobs whose status has changed and has not been reported by the shell. OPERANDS
Specifies the jobs for which the status is to be displayed. If no job_id operand is given, the status information for all jobs is dis- played. The format of job_id is described in the Jobs section of the ksh(1) reference page. DESCRIPTION
The jobs utility displays the status of jobs that were started in the current shell environment. When jobs reports the termination status of a job, the shell removes its process ID from the list of those "known in the current shell exe- cution environment". See the Jobs section of the ksh(1) reference page. RESTRICTIONS
The jobs utility does not work as expected when it is operating in its own utility execution environment because that environment has no applicable jobs to manipulate. EXIT STATUS
The following exit values are returned: Successful completion. An error occurred. ENVIRONMENT VARIABLES
The following environment variables affect the execution of jobs: 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 vari- ables 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 characters in arguments). Determines the locale used to affect the format and contents of diagnostic messages written to standard error and informative messages written to standard output. Determines the location of message catalogues for the processing of LC_MESSAGES. SEE ALSO
Commands: bg(1), csh(1), fg(1), kill(1), ksh(1), sh(1p), wait(1) Standards: standards(5) jobs(1)
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