Show contents of many files

command linefiles

From the command line, what is the easiest way to show the contents of multiple files? My directory looks like below.

./WtCgikkCFHmmuXQXp0FkZjVrnJSU64Jb9WSyZ52b
./xdIwVHnHY7dnuM9zcPDYQGZFdoVORPyMVD2IzjgM
./GZnATXO1e5Hh3Bz1bhgJjjwheIjjZqtnXR0hfOyj
./mWz7ehBNoTZmtDh8JG6sxw2lMJFwIovPzxDGECUY
./JN65F5v3RL2ilHPqNSx9N9D4lvVpqpbJ9lASd8TJ
./At9PS4y4nTiXUO0Z0USnbYkTPBla1msQRpwuruqE
./YiPyMZPCaUDZTiTczAvWII9bJrUqLXCFtH2pXEA2
./JoakdlbRFPwAvWp1d4n8RvMoyMeizCoiriL2Sn2U
./wFPWZUus8Yu7UtESGABLCoqDg36cT90USO0xuyUr
./qseI9PgV1EJfZCDyGGeVytajqG7JeX0r7eA5S1JW
./zgFJpNgXyCsaVh38aCuMGuzHwIbwSNB6rQDdh27x
./.htaccess

Now I'd like to view the contents of all files except .htaccess. It might look something like:

WtCgikkCFHmmuXQXp0FkZjVrnJSU64Jb9WSyZ52b:
Contents of file WtCgikkCFHmmuXQXp0FkZjVrnJSU64Jb9WSyZ52b.

xdIwVHnHY7dnuM9zcPDYQGZFdoVORPyMVD2IzjgM:
Contents of file xdIwVHnHY7dnuM9zcPDYQGZFdoVORPyMVD2IzjgM.

[...]

I think this should be doable with a combination of find, xargs and cat, but I haven't figured out how. Thanks for your time!

Best Answer

The two standard commands head and tail print a header with the file name if you pass them more than one file argument. To print the whole file, use tail -n +1 (print from the first line onwards, i.e. everything).

Here, it looks like you want to see every file except the single one whose name begins with a dot. Dot files are “hidden” under unix: they don't appear in the default output of ls or in a wildcard match. So matching every non-hidden files is done with just *.

tail -n +1 *

(Strictly speaking, tail -n +1 -- * is needed in case one of the file names begins with a -.)

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Rename files to change punctuation and numbering

You can use the prename command to rename files based on a transformation written in Perl.

Let's start simple. To rename all the .jpg files in a directory, changing all - to _, we can just use the s operator (we could also use tr). The Perl code is executed to transform each file name.

prename 's!-!_!g' *.jpg

To change the number sequence(s) at the end to a simple counter, we introduce a counter variable. I use the global variable $a as a counter (introducing extra variables is more complicated). The regular expression (\.[^/.]*)$ matches the file extension, and $1 in the replacement text stands for what the parenthesized group matched.

prename 's!-!_!g; ++$a; s!_[0-9_]+(\.[^/.]*)$!_$a$1!' *.jpg

Note that the files are renamed in the order given by the file name arguments, i.e. the order of expansion of *.jpg determines the numbering of the files.

Alternatively, we can initialize the counter explicitly with a BEGIN block.

prename 'BEGIN {$a = 1;} s!-!_!g; s!_[0-9_]+(\.[^/.]*)$!_$a$1!; ++$a;' *.jpg

To perform this in every subdirectory of the current directory, call find.

find -type d -exec sh -c 'cd "$1" && prename "$0" *.jpg' 's!-!_!g; ++$a; s!_[0-9_]+(\.[^/.]*)$!_$a$1!' {} \;

Split a JSON array into multiple files

From this SO thread:

jq -cr 'keys[] as $k | "\($k)\n\(.[$k])"' input.json | while read -r key; do
  fname=$(jq --raw-output ".[$key].billingAccountNumber" input.json)
  read -r item
  printf '%s\n' "$item" > "./$fname"
done

Best Answer

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Rename files to change punctuation and numbering

Split a JSON array into multiple files

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