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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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fg(1)							      General Commands Manual							     fg(1)

NAME
fg - Runs jobs in the foreground SYNOPSIS
fg [job_id...] Note The C shell has a built-in version of the fg 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/fg. 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: fg: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
None OPERANDS
Specifies the job to be run as a foreground job. If no job_id operand is given, the job_id for the job that was most recently suspended, placed in the background or run as a background job is used. The format of job_id is described in the Jobs section of the ksh(1) reference page. DESCRIPTION
If job control is enabled (see the description of set -m in the ksh(1) reference page), the fg utility moves a background job from the cur- rent environment into the foreground. Using fg to place a job into the foreground removes its process ID from the list of those "known in the current shell execution environ- ment"; see the Jobs section of the ksh(1) reference page. RESTRICTIONS
If job control is disabled, the fg utility exits with an error and no job is placed in the foreground. The fg 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 fg: 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. Determines the location of message catalogues for the processing of LC_MESSAGES. SEE ALSO
Commands: bg(1), csh(1), jobs(1), kill(1), ksh(1), sh(1p), wait(1) Standards: standards(5) fg(1)
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