Bash – find -exec with multiple commands

bashfind

I am trying to use find -exec with multiple commands without any success. Does anybody know if commands such as the following are possible?

find *.txt -exec echo "$(tail -1 '{}'),$(ls '{}')" \;

Basically, I am trying to print the last line of each txt file in the current directory and print at the end of the line, a comma followed by the filename.

Best Answer

find accepts multiple -exec portions to the command. For example:

find . -name "*.txt" -exec echo {} \; -exec grep banana {} \;

Note that in this case the second command will only run if the first one returns successfully, as mentioned by @Caleb. If you want both commands to run regardless of their success or failure, you could use this construct:

find . -name "*.txt" \( -exec echo {} \; -o -exec true \; \) -exec grep banana {} \;

Related Solutions

Bash – How to exclude all “permission denied” messages from “find”

Use:

find . 2>/dev/null > files_and_folders

This hides not just the Permission denied errors, of course, but all error messages.

If you really want to keep other possible errors, such as too many hops on a symlink, but not the permission denied ones, then you'd probably have to take a flying guess that you don't have many files called 'permission denied' and try:

find . 2>&1 | grep -v 'Permission denied' > files_and_folders

If you strictly want to filter just standard error, you can use the more elaborate construction:

find . 2>&1 > files_and_folders | grep -v 'Permission denied' >&2

The I/O redirection on the find command is: 2>&1 > files_and_folders |. The pipe redirects standard output to the grep command and is applied first. The 2>&1 sends standard error to the same place as standard output (the pipe). The > files_and_folders sends standard output (but not standard error) to a file. The net result is that messages written to standard error are sent down the pipe and the regular output of find is written to the file. The grep filters the standard output (you can decide how selective you want it to be, and may have to change the spelling depending on locale and O/S) and the final >&2 means that the surviving error messages (written to standard output) go to standard error once more. The final redirection could be regarded as optional at the terminal, but would be a very good idea to use it in a script so that error messages appear on standard error.

There are endless variations on this theme, depending on what you want to do. This will work on any variant of Unix with any Bourne shell derivative (Bash, Korn, …) and any POSIX-compliant version of find.

If you wish to adapt to the specific version of find you have on your system, there may be alternative options available. GNU find in particular has a myriad options not available in other versions — see the currently accepted answer for one such set of options.

Bash – How to redirect and append both standard output and standard error to a file with Bash

cmd >>file.txt 2>&1

Bash executes the redirects from left to right as follows:

>>file.txt: Open file.txt in append mode and redirect stdout there.
2>&1: Redirect stderr to "where stdout is currently going". In this case, that is a file opened in append mode. In other words, the &1 reuses the file descriptor which stdout currently uses.

Best Answer

Related Solutions

Bash – How to exclude all “permission denied” messages from “find”

Bash – How to redirect and append both standard output and standard error to a file with Bash

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