tag_file.txt

PROBLEM: tag a file, at the top of the file, with the base name of the parent directory.

SOLUTION 1 -- non-empty files:

$ bn=${PWD##*/}    ## bn: basename

$ sed -i '1s/^/'"$bn"'\n/' <filename>

SOLUTION 2a -- empty files:

## sed fails on empty files; solution:

$ printf "${PWD##*/}\n" >> <filename>

SOLUTION 2b -- recurse over directory:

$ for file in *; do printf "${PWD##*/}\n" >> $file; done


==============================================================================

PROBLEM: tag a file, at the top of the file, with the base name of the parent directory.

[victoria@victoria Cancer]$ pwd
    /home/victoria/Cancer

----------------------------------------
SOLUTION 1 -- non-empty files:

[victoria@victoria Cancer]$ l

    total 8.0K
    -rw-r--r-- 1 victoria victoria 33 Mar 23 17:38 cancer1
    -rw-r--r-- 1 victoria victoria 26 Mar 23 17:39 cancer2

[victoria@victoria Cancer]$ cat cancer1

    aaa
    bbb

[victoria@victoria Cancer]$ cat cancer2

    ccc
    ddd

[victoria@victoria Cancer]$ ## bn: basename

[victoria@victoria Cancer]$ bn=${PWD##*/}

[victoria@victoria Cancer]$ pwd
    /home/victoria/Cancer

[victoria@victoria Cancer]$ echo $bn
    Cancer

[victoria@victoria Cancer]$ sed -i '1s/^/tag: '"$bn"'\n/' cancer1
[victoria@victoria Cancer]$ sed -i '1s/^/tag: '"$bn"'\n/' cancer2

[victoria@victoria Cancer]$ cat cancer1

    tag: Cancer
    aaa
    bbb

[victoria@victoria Cancer]$ cat cancer2

    tag: Cancer
    ccc
    ddd

[victoria@victoria Cancer]$ rm -f cancer*

----------------------------------------
SOLUTION 2a -- empty files:

[victoria@victoria Cancer]$ touch cancer1
[victoria@victoria Cancer]$ touch cancer2

[victoria@victoria Cancer]$ cat cancer1
[victoria@victoria Cancer]$ cat cancer2

## sed fails on empty files:

[victoria@victoria Cancer]$ sed -i '1s/^/tag: '"$bn"'\n/' cancer1
[victoria@victoria Cancer]$ sed -i '1s/^/tag: '"$bn"'\n/' cancer2

[victoria@victoria Cancer]$ cat cancer1
[victoria@victoria Cancer]$ cat cancer2

## Solution:

[victoria@victoria Cancer]$ printf "tag: ${PWD##*/}\n" >> cancer1
[victoria@victoria Cancer]$ printf "tag: ${PWD##*/}\n" >> cancer2

[victoria@victoria Cancer]$ cat cancer1

    tag: Cancer

[victoria@victoria Cancer]$ cat cancer2

    tag: Cancer

[victoria@victoria Cancer]$ rm -f cancer*

----------------------------------------
SOLUTION 2b -- recurse over directory:

[victoria@victoria Cancer]$ touch cancer1
[victoria@victoria Cancer]$ touch cancer2

[victoria@victoria Cancer]$ for file in *; do printf "tag: ${PWD##*/}\n" >> $file; done

[victoria@victoria Cancer]$ cat cancer1

    tag: Cancer

[victoria@victoria Cancer]$ cat cancer2

    tag: Cancer

## Again:

[victoria@victoria Cancer]$ for file in *; do printf "tag: ${PWD##*/}\n" >> $file; done

[victoria@victoria Cancer]$ cat cancer1

    tag: Cancer
    tag: Cancer

[victoria@victoria Cancer]$ cat cancer2

    tag: Cancer
    tag: Cancer

[victoria@victoria Cancer]$

----------------------------------------

Solutions loosely cobbled from:

A1 in: http://stackoverflow.com/questions/10654135/take-the-last-part-of-the-folder-path-in-shell

A1, A2 in: http://stackoverflow.com/questions/9533679/how-to-insert-a-text-at-the-beginning-of-a-file

A2 in: https://unix.stackexchange.com/questions/69112/how-can-i-use-variables-when-doing-a-sed/69113#69113

https://www.cyberciti.biz/faq/bash-loop-over-file/

==============================================================================

ADDENDA:

echo $PWD
    /home/victoria

printf "${PWD##*/}\n"    ## need the newline ( \n ) to see the output
    victoria

pwd
    /home/victoria

dirname $(pwd)
    /home/victoria

basename $(pwd)
    victoria

dirname $PWD
    /home

basename $PWD
    victoria

------------------------------------------------------------------------------

Note: I considered simply using

    basename $PWD

or

    basename $(pwd)

... however, my rationale for

    ${PWD##*/}

is found here:

http://stackoverflow.com/questions/1371261/get-current-directory-name-without-full-path-in-bash-script/1371283#1371283

"No need for basename, and especially no need for a subshell running pwd (which adds an extra,
and expensive, fork operation); the shell can do this internally using parameter expansion ..."

==============================================================================

http://lists.claws-mail.org/pipermail/users/2017-March/thread.html#18865
http://lists.claws-mail.org/pipermail/users/2017-March/018865.html

Q. re: tags (tagging locally-saved messages for use outside Claws)

printf is faster with or without bash:

$ cat dash.sh

    #!/bin/dash
    for i in `seq 1 1000`
    do
      basename "$PWD" >/dev/null
    done
    exit

$ cat bash.sh

    #!/bin/bash
    for i in `seq 1 1000`
    do
      printf "${PWD##*/}\n" >/dev/null
    done
    exit


$ time ./dash.sh

    real	0m0.468s
    user	0m0.010s
    sys	0m0.053s

$ time ./bash.sh

    real	0m0.042s
    user	0m0.033s
    sys	0m0.007s


0.468/0.042 = 11.1428 real-time difference,
[basename "$PWD"] vs. [printf "${PWD##*/}\n"]

  http://stackoverflow.com/questions/556405/what-do-real-user-and-sys-mean-in-the-output-of-time1

  Real is wall clock time - time from start to finish of the call. This is all
  elapsed time including time slices used by other processes and time the
  process spends blocked (for example if it is waiting for I/O to complete).

----------------------------------------

$ cat dash.sh

    #!/bin/dash
    for i in `seq 1 1000`
    do
      printf "${PWD##*/}\n" >/dev/null
    done
    exit

$ cat bash.sh

    #!/bin/bash
    for i in `seq 1 1000`
    do
      basename "$PWD" >/dev/null
    done
    exit


$ time ./dash.sh

    real	0m0.017s
    user	0m0.007s
    sys	0m0.007s

$ time ./bash.sh

    real	0m0.531s
    user	0m0.030s
    sys	0m0.063s

0.531/.017 = 31.2352-fold difference,
[basename "$PWD"] vs. [printf "${PWD##*/}\n"]

==============================================================================