You can use the -i flag correctly by providing it with a suffix to add to the backed-up file. Extending your example: sed -i.bu ‘s/oldword/newword/’ file1.txt Will give you two files: one with the name file1.txt that contains the substitution, and one with the name file1.txt.bu that has the original content. Mildly dangerous If you … Read more
The problem is with slashes: your variable contains them and the final command will be something like sed “s/string/path/to/something/g”, containing way too many slashes. Since sed can take any char as delimiter (without having to declare the new delimiter), you can try using another one that doesn’t appear in your replacement string: replacement=”/my/path” sed –expression … Read more
Just keep it simple 🙂 grep + echo should suffice: grep -qxF ‘include “/configs/projectname.conf”‘ foo.bar || echo ‘include “/configs/projectname.conf”‘ >> foo.bar -q be quiet -x match the whole line -F pattern is a plain string https://linux.die.net/man/1/grep Edit: incorporated @cerin and @thijs-wouters suggestions.
A sample command that exhibits the symptom: sed ‘s/./@/’ <<<$’\xfc’ fails, because byte 0xfc is not a valid UTF-8 char. Note that, by contrast, GNU sed (Linux, but also installable on macOS) simply passes the invalid byte through, without reporting an error. Using the formerly accepted answer is an option if you don’t mind losing … Read more
This can be done with a sed one-liner: sed ‘/^#/d’ This says, “find all lines that start with # and delete them, leaving everything else.”
Using sed, just for variety: ls -l | sed -n 2p Using this alternative, which looks more efficient since it stops reading the input when the required line is printed, may generate a SIGPIPE in the feeding process, which may in turn generate an unwanted error message: ls -l | sed -n -e ‘2{p;q}’ I’ve … Read more
you can try with awk: awk ‘/blah/{getline; print}’ logfile
I’m surprised nobody has mentioned the -exec argument to find, which is intended for this type of use-case, although it will start a process for each matching file name: find . -type f -name ‘xa*’ -exec sed -i ‘s/asd/dsg/g’ {} \; Alternatively, one could use xargs, which will invoke fewer processes: find . -type f … Read more
You can use tail command as follows: tail -100 <log file> > newLogfile Now last 100 lines will be present in newLogfile EDIT: More recent versions of tail as mentioned by twalberg use command: tail -n 100 <log file> > newLogfile
In order of appearance, the languages are sed, awk, perl, python. The sed program is a stream editor and is designed to apply the actions from a script to each line (or, more generally, to specified ranges of lines) of the input file or files. Its language is based on ed, the Unix editor, and … Read more