Is there another simple way to append line to end of file other than `>>`?

Question

Recently I'm echoing short sentences to a tree_hole file.

I was using echo 'something' >> tree_hole to do this job.

But I was always worried of what if I mis-input of > instead of >>, since I did this often.

So I made a global bash func of my own in the bashrc:

function th { echo "$1" >> /Users/zen1/zen/pythonstudy/tree_hole; }
export -f th

But I'm wondering if there is another simple way to append lines to the end of a file. Because I may need to use that often in other occasions.

Is there any?

Answer 1

Set the shell's noclobber option:

bash-3.2$ set -o noclobber
bash-3.2$ echo hello >foo
bash-3.2$ echo hello >foo
bash: foo: cannot overwrite existing file
bash-3.2$ 

Answer 2

If you are worried your file will be damaged by > operator you can change your file attribute to append only:
In ext2/ext3/ext4 filesystem: chattr +a file.txt
In XFS filesystem: echo chattr +a | xfs_io file.txt

And if you want a function, I made a function for myself already (I used it in service file for logging outputs), You can change it for your purpose:

# This function redirect logs to file or terminal or both!
#@ USAGE: log option data
# To the file     -f file
# To the terminal -t
function log(){
        read -r data       # Read data from pipe line

        [[ -z ${indata} ]] && return 1    # Return 1 if data is null

        # Log to /var/log/messages
        logger -i -t SOFTWARE ${data}

        # While loop for traveling on the arguments
        while [[ ! -z "$*" ]]; do
                case "$1" in
                        -t)
                                # Writting data to the terminal
                                printf "%s\n" "${data}"
                                ;;
                        -f) 
                                # Writting (appending) data to given log file address
                                fileadd=$2
                                printf "%s %s\n" "[$(date +"%D %T")] ${data}" >> ${fileadd}
                                ;;
                        *)
                                ;;
                esac
                shift           # Shifting arguments
        done
}

Answer 3

Use tee with the append option:

foo | tee -a some-file
# or
tee -a some-file <<EOF
blah blah
EOF
# or 
tee -a some-file <<<"blah blah"

Answer 4

many programs that can open files for overwriting can alternatively open them for append, eg gnu dd.

dd conv=notrunc oflag=append of=file

it can read stdin or a file named in the if= parameter add 2>/dev/null to suppress the byte count.

Answer 5

I'd like use a sed (even with backup-copy - see extention after -i):

sed -i.bak '$ a\something' /Users/zen1/zen/pythonstudy/tree_hole

Answer 6

You can always seek through the file in other ways...

seq 10000000 >f
{ wc -l >&2; echo new line\!; } <>f >&0; \
{ wc -l >&2; echo new line\!; } <>f >&0; \
{ wc -l >&2; echo new line\!; } <>f >&0; \
{ wc -l >&2; echo new line\!; } <>f >&0; \
{ wc -l >&2; echo new line\!; } <>f >&0; \
wc -l f; tail f

...that weird looking sequence prints:

10000000
10000001
10000002
10000003
10000004
10000005 f
9999996
9999997
9999998
9999999
10000000
new line!
new line!
new line!
new line!
new line!

But that's kinda silly.

A more useful example could look like:

 apnd() if    shift
        then  wc -l  >&2
              printf "$@"
        fi    <>"$1" >&0

You can call it like:

 apnd /path/to/file          \
      "${printf_fmt_string}" \
       arbitrary list of strings

And you'd wind up with a count of file's lines written to stderr just before the append action takes place.