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Full Discussion: AWK How to replace a field using 2 shell variables?
Top Forums Shell Programming and Scripting AWK How to replace a field using 2 shell variables? Post 302542768 by basalt on Thursday 28th of July 2011 02:02:21 PM
Old 07-28-2011
AWK How to replace a field using 2 shell variables?
Hello everybody:
I want to replace any field $2 of any file line (f.i. test.txt) matching $1 with a shell variable.

Code:
$ cat test.txt    
F       0
B       A
H       -12.33

Now I'm going to ask the value of variable B:
Code:
$ SEARCHVAR=B
$ OLDVAL=$(awk -v SEARCHVAR="$SEARCHVAR" '$1==SEARCHVAR {print $2}' test.txt)
$ echo $OLDVAL
A

And finally i tries to replace this value ("A") from field 2 by another shell variable with "10", using awk again:
Code:
$ NEWVAL=10
$ awk -v SEARCHVAR="$SEARCHVAR" OLDVAL="$OLDVAL" NEWVAL="$NEWVAL" '{if($1==SEARCHVAR && $2==OLDVAL) sub{OLDVAL,NEWVAL,$2} {print}}' test.txt

Unfortunately I only gets fatal error messages again & again.
Can you help me, please?
Thanks all in advace.
Last edited by basalt; 07-28-2011 at 04:42 PM..
 

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LEARN ABOUT XFREE86

chsh

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)
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