Can I search/replace in multiple .txt files quickly from Terminal? [duplicate]

Answer 1

sed -i 's/--/–/g' *.txt ought to work. The -i flag to sed makes it act on the files in-place, the s stands for substitute, and the g makes it replace multiple occurrences of the pattern on the same line. Look up sed's documentation for more information.

EDIT: This works on GNU/Linux; it turns out that the syntax is slightly different on OSX (see comments and accepted answer).

Answer 2

GNU sed:

sed -i 's/--/—/g' *.txt

OSX BSD sed:

You need to specify a backup file extension. To create a backup file with the extension: .txt.bak:

sed -i '.bak' 's/--/—/g' *.txt

To completely replace the files, specify an empty extension:

sed -i '' 's/--/—/g' *.txt