Command to append line to a text file without opening an editor

Question

Assuming i have a line that i want to add to a file without opening an editor.

How could i append this line

alias list='ls -cl --group-directories-first'

to this file

config.fish

score 313 · Accepted Answer · edited Apr 13 '17 at 12:24

313

You can append a line of text to a file by using the >> operator:

echo "hello world" >> my_file.txt

or in your case

echo "alias list='ls -cl --group-directories-first'" >> config.fish

Please take note of the different types of quotes.

edited Apr 13 '17 at 12:24

Community

1

answered Jan 14 '11 at 19:09

Stefano Palazzo

88,393

Sergiy Kolodyazhnyy · Answer 2 · 2019-12-23T07:14:54.940

There's plenty of methods of appending to file without opening text editors, particularly via multiple available text processing utilities in Ubuntu. In general, anything that allows us to perform open() syscall with O_APPEND flag added, can be used to append to a file.

GNU version of dd utility can append data to file with conv=notrunc oflag=append
```
printf "\nalias list='ls -cl --group-directories-first'\n" | dd conv=notrunc oflag=append bs=1 of=config.fish
```
Portably we could use something like this on the right side of pipeline:
```
dd conv=notrunc seek=$(wc -c < testFile.txt) bs=1 of=testFile.txt
```
Note the use of bs=1 , which is to prevent short reads from pipeline
The tee command can be used when you need to append to file and send it to stdout or to next command in pipeline
```
tee -a config.fish <<< "alias list='ls -cl --group-directories-first'"
```

awk has append operator >> which is also portable and defined by POSIX specifications

awk 'BEGIN{ printf "alias list=\x27ls -cl --group-directories-first\x27\n" >> "config.fish"  }'

We can combine sed's flag $ to match the last line with a for appending and -i for in-place editing.
```
sed -i '$a alias list='"'"'ls -cl --group-directories-first'"'" config.fish
```
We could even implement something like dd in Python 3:

    #!/usr/bin/env python3
    # read bytes from stdin, append to specified file
    import sys

    with open(sys.argv[1],'ab') as f:
         f.write(sys.stdin.buffer.read())

Command to append line to a text file without opening an editor

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