CODEWITHSUNDEEP
tcl
Mateusz K
Mateusz K

Reputation: 15

How do i replace line in text file?

How can i replace a specific line in text file in Tcl for example:

a.txt contains:

John
Elton

and I need to replace the contents to b.txt which contains:

John
Belushi

In Bash, I know that I can use: sed '2s/.*/Belushi/' a.txt > b.txt. But it doesn't work.

Upvotes: 0

Views: 1166

Answers (2)

Donal Fellows
Donal Fellows

Reputation: 137577

The pure Tcl way of doing the replacement is this:

# Read the lines into a Tcl list
set f [open "a.txt"]
set lines [split [read $f] "\n"]
close $f

# Do the replacement
lset lines 1 "Belushi"

# Write the lines back out
set f [open "b.txt" w]
puts -nonewline $f [join $lines "\n"]
close $f

The only vaguely tricky bit is that you need -nonewline or you'll get an extra newline from the puts; we're supplying all the newlines that we want it to produce already.

Upvotes: 1

Dinesh
Dinesh

Reputation: 16428

There can be many ways. If you want to use the same sed command, you can very well do it with the exec command

#!/usr/bin/tclsh
exec sed {2s/.*/Belushi/} a.txt > b.txt

The reason why we quoted this with the braces instead of single quotes is to prevent any substitutions.

Upvotes: 1

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