Remove occurences of small words within a string

Question

I\'m trying to remove a specific word from a string. I can\'t do a simple global string replace for \"the\" to empty string as \"the\" could be part of a word in the string.

Answer 1

Take a look at this sed:

$ string='the_ad_an_feta_cfr_era_the_iop_the'
$ sed -E -e ':a' -e 's/(^|_)(the|an|is|feta)(_|$)/\1/g;ta' -e 's/_$//' <<< "$string"
ad_cfr_era_iop

Note that the behavior of sed differs between Unix variants. Your sed seems to require newlines after labels (or multiple -e options). Further reading:

• BSD/macOS Sed vs. GNU Sed vs. the POSIX Sed specification
• Differences between sed on Mac OSX and other “standard” sed?

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Version without labels which is essentially the same as @Cyrus' answer but supports "items" with spaces:

$ string='the_ad_an_feta_cfr_era_the cfr_the_iop_the'
$ sed -E -e 's/_/__/g;s/(^|_)(the|an|is|feta)(_|$)//g;s/_+/_/g;s/^_//;s/_$//' <<< "$string"
ad_cfr_era_the cfr_iop