onceupon / bash-oneliner Goto Github PK

All in the title.

Thank you for your great work.

Issue closed

Hi,

First thing I just want to congratulate you on this great list. I was looking for something like this for a while and I'm glad to see that you did a fantastic job compiling this list.
Now I just want to let you know about a typo I've noticed Terminal Tricks / Change case: https://github.com/onceupon/Bash-Oneliner#change-case
Esc + l changes the text to lowercase not uppercase.

Remove the ‘ ’ style quotes and replace with ASCII single quotes.

README.md:106:3:# ‘[]’ serves to match the character from a range.
README.md:106:8:# ‘[]’ serves to match the character from a range.
README.md:109:3:# ‘{}’ can be used to match filenames with more than one patterns
README.md:109:8:# ‘{}’ can be used to match filenames with more than one patterns
README.md:287:6:grep ‘[0-9]\{3\}’
README.md:287:19:grep ‘[0-9]\{3\}’
README.md:289:9:grep -E ‘[0-9]{3}’
README.md:289:20:grep -E ‘[0-9]{3}’
README.md:291:9:grep -P ‘\d{3}’
README.md:291:17:grep -P ‘\d{3}’
README.md:405:6:grep ‘colou?r’
README.md:405:16:grep ‘colou?r’

printf '‘’' | od -a

0000000   b nul can   b nul  em
0000006

The program pgrep is not grep -P.
pgrep was removed from the grep repo in 2000. [0]

[0] https://git.savannah.gnu.org/cgit/grep.git/tree/ChangeLog-2009#n2069

factor is not a bash built-in nor a bash plugin. It's a program in its own right, independent of bash, part of gnu coreutils, and is related to bash about as much as, say, a video- or music player is.

busybox provides a factor app too, alas it's much more limited in allowable number range than the coreutils version, which I tend to use as quick poor person's CPU benchmark:

time factor 1234567890123456789012345678901

As this yields two large prime factors, it takes a reasonable (as in measurable) time. Because the number is easy to memorize, and can be shortcut nicely with copy-and-paste, it serves as a nice rough evaluation of CPU performance - depending on machine between about 150ms for notebooks and desktop computers, to 400 to 1000 and above ms for ARM SBC. My WiFi router takes about 4 seconds, comparable to oldish ARM SBCs.

Nevertheless, factor still isn't related to bash.

Error in the README "Variable substitution within quotes" section.

# doubled single quotes act as double quotes making variables expand
echo ''$foo''
# bar

Technically it doesn't act as double quotes, but acts as if there were no quotes at all.
The difference lies on word splitting.
An example with mkdir can show the difference:

foo='a b'
mkdir $foo # Expected result: two directories, 'a' 'b'
mkdir ''$foo'' # Expected result: two directories, 'a' 'b'
mkdir "$foo" # Expected result: one directory, 'a b'

's/singer/single/'

First off, at the beginning of the "data wrangling" section, in the example output for the look command, you say that you are running the command look phy|head -n 10 but the output does not show words beginning with phy. It instead shows word beginning with Phi. I would change this section to:

##### Print some words that start with a particular string (e.g. words start with 'phy')
```bash
# If file is not specified, the file /usr/share/dict/words is used.
look phy|head -n 10
# Phyciodes
# phycite
# Phycitidae
# phycitol
# phycochromaceae
# phycochromaceous
# phycochrome
# Phycochromophyceae
# phycochromophyceous
# phycocyanin
```

Secondly, I would add some usage of the command comm to find between two sorted files common lines, lines in one file but not in another; something like:

##### Find common/differing lines
The command `comm` can be used to find lines common to two files (intersection), or to find lines in one file and not in another file. **Warning**: input files must be sorted.
```bash
# Sort input before handing to comm; the -o option lets you sort a file in-place
sort -o bad-actors.txt bad-actors.txt
sort -o invited-guests.txt invited-guests.txt
# Find lines in both files
comm -12 bad-actors.txt invited-guests.txt
# Find lines in invited-guests.txt that are NOT in bad-actors.txt
comm -13 bad-actors.txt invited-guests.txt
# Find lines that are in good-actors.txt but NOT in invited-guests.txt.
# Note that since we didn't sort good-actors.txt above, we need to sort it before handing it to comm
comm -23 <(sort good-actors.txt) invited-guests.txt
```

This can also be combined with use of jq to do things like "compare these two json arrays of strings, and find the strings that are in both arrays".

Nice collection of examples! Thank you for your work!

Did you consider the conversion of Bash-Oneliner to Jupyter Notebook tree as an option?
This can provide more interactivity and structuralism for examples