String substitution is not working in shell script

Kauser — Thu, 25 Mar 2021 12:07:37 GMT

Dear concern,

I've write following script.

bash-4.2$ cat truncate.sh #!/bin/sh LOGPATH="/wls_home/swig_atm/SwitchDbg" ARCPATH="/wls_home/swig_atm/SwitchDbgArc" for i in $LOGPATH/MSG*log do if [ ! -e $i ]; then break ; fi #echo "For filename : $i" filename=`basename $i .log` dirname=`echo ${filename:4}` ofilename=`date +%H%M` #echo "target filename = $ARCPATH/$dirname/$dirname.$ofilename" if [ -e $ARCPATH/$dirname ];then mv $i "$ARCPATH/$dirname/$dirname.$ofilename" else mkdir -p $ARCPATH/$dirname mv $i "$ARCPATH/$dirname/$dirname.$ofilename" fi done

But String substitution is not working in below arrow mentioned secton. Please assist me,

bash-4.2$ sh -x truncate.sh + LOGPATH=/wls_home/swig_atm/SwitchDbg + ARCPATH=/wls_home/swig_atm/SwitchDbgArc + [ ! -e /wls_home/swig_atm/SwitchDbg/MSG_23March2021.log ] + + basename /wls_home/swig_atm/SwitchDbg/MSG_23March2021.log .log filename=MSG_23March2021 + truncate.sh[10]: ${filename:4}: The specified substitution is not valid for this command.===========>String substitution is not working dirname= + + date +%H%M ofilename=1743 + [ -e /wls_home/swig_atm/SwitchDbgArc/ ] + mv /wls_home/swig_atm/SwitchDbg/MSG_23March2021.log /wls_home/swig_atm/SwitchDbgArc//.1743

Re: String substitution is not working in shell script

Steven Schweda — Thu, 25 Mar 2021 21:57:24 GMT

> [...] String substitution is not working [...]

> bash-4.2$ [...]

You may be using "bash" interactively, but your script uses a
different shell (with different features):

> #!/bin/sh

That kind of parameter substitution is not a feature of that shell.

man sh-posix # Look for "Parameter Substitution".

There are alternatives . For example:

rux$ echo ${filename}
MSG_23March2021

rux$ echo ${filename#????}
23March2021

Or, perhaps more generally:

rux$ echo ${filename#*_}
23March2021

As usual, many things are possible. (But not everything works with
every shell.)

Also, in:
dirname=`echo ${filename:4}`
what does
`echo `
buy you? Why not?:

dirname=${filename#????}

Alternatively, you could change your script to use "bash" (wherever
it is) instead of "/bin/sh", but I'd stick with "/bin/sh" for
portability/reliability.

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String substitution is not working in shell script

Re: String substitution is not working in shell script