by hand

[common] Said of an operation (especially a repetitive, trivial, and/or tedious one) that ought to be performed automatically by the computer, but which a hacker instead has to step tediously through. "My mailer doesn't have a command to include the text of the message I'm replying to, so I have to do it by hand." This does not necessarily mean the speaker has to retype a copy of the message; it might refer to, say, dropping into a subshell from the mailer, making a copy of one's mailbox file, reading that into an editor, locating the top and bottom of the message in question, deleting the rest of the file, inserting `>' characters on each line, writing the file, leaving the editor, returning to the mailer, reading the file in, and later remembering to delete the file. Compare {eyeball search}.
[common] By extension, writing code which does something in an explicit or low-level way for which a presupplied library routine ought to have been available. "This cretinous B-tree library doesn't supply a decent iterator, so I'm having to walk the trees by hand."