CODEWITHSUNDEEP
linuxtclexpect
Mike.G
Mike.G

Reputation: 125

How to delete lines matching a pattern from a file using Tcl/Expect

I am trying to understand how to work with expect.

I want to check if a file has a certain string in it and if it does contain it than delete the whole line, i know how i would do that with bash with if and grep, but im fairly new to expect and i am having issues with getting it to work the basic idea is this ( in bash script ) 

if grep -q "string" "file";
then
    echo "something is getting deleted".
    sed -i "something"/d "file"
    echo Starting SCP protocol
else
    echo "something was not found"
    echo Starting SCP protocol. 
fi

Thanks in advance.

Upvotes: 0

Views: 4593

Answers (2)

glenn jackman
glenn jackman

Reputation: 247210

Since @whjm deleted his answer, here's a pure-Tcl way to accomplish your task:

set filename "file"
set found false
set fh [open $filename r]
while {[gets $fh line] != -1} {
    if {[regexp {string} $line]} {
        puts "something is getting deleted"
        close $fh

        set fh_in [open $filename r]
        set fh_out [file tempfile tmpname]
        while {[gets $fh_in line] != -1} {
            if {![regexp {something} $line]} {
                puts $fh_out $line
            }
        }
        close $fh_in
        close $fh_out
        file rename -force $tmpname $filename

        set found true
        break        
    }
}
if {!$found} {close $fh}
puts "Starting SCP protocol"

Upvotes: 1

glenn jackman
glenn jackman

Reputation: 247210

Another approach: using Tcl as a glue language, like the shell, calling out to system tools:

if {[catch {exec grep -q "string" "file"} output] == 0} {
    puts "something is getting deleted".
    exec sed -i "something"/d "file"
} else {
    puts "something was not found"
}
puts "Starting SCP protocol"

See https://wiki.tcl.tk/1039#pagetoce3a5e27b for a thorough explanation of using catch and exec

More current Tcl would look like

try {
    exec grep -q "string" "file"
    puts "something is getting deleted".
    exec sed -i "something"/d "file"
} on error {} {
    puts "something was not found"
}
puts "Starting SCP protocol"

Upvotes: 1

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