Command Like head for Line Truncation

software-rectext processing

Linux's head selects a number of lines from the top of a file. Is there a command that selects a number of characters from the front of a line?

The use case behind the question is this: I want to head the first 10 lines from a file, but each of those 10 lines is extremely long and contain lots of white space, making it hard to discern where the line breaks are.

It would be much easier to get a general idea of the contents of the file if I could head the first 10 lines, but only view the first 50 characters of each line.

Best Answer

Try cut:

head -n 10 bigfile | cut -c 1-50

Related Solutions

Text Processing – Sort but Keep Header Line at the Top

Stealing Andy's idea and making it a function so it's easier to use:

# print the header (the first line of input)
# and then run the specified command on the body (the rest of the input)
# use it in a pipeline, e.g. ps | body grep somepattern
body() {
    IFS= read -r header
    printf '%s\n' "$header"
    "$@"
}

Now I can do:

$ ps -o pid,comm | body sort -k2
  PID COMMAND
24759 bash
31276 bash
31032 less
31177 less
31020 man
31167 man
...

$ ps -o pid,comm | body grep less
  PID COMMAND
31032 less
31177 less

Find a specific string and delete the whole structure

The right way to do this is to use a proper XML parser. However, in this case, the following might work as a workaround:

Remove all blank lines from the file:
```
sed -i '/^\s*$/d' file
```
Add a blank line before each <doc>:
```
sed -i 's/<doc/\n\n<doc/' file 
```
User Perl's "paragraph mode" where "lines" are defined as "paragraphs" (sections of text preceded by an empty line):
```
perl -00 -ne 'print unless /[ĂĹľşÄ]/' file > newfile
```
Or, to make the replacements in the original file:
```
perl -i.bak -00 -ne 'print unless /[ĂĹľşÄ]/' file
```

IMPORTANT: This assumes a well-structured file where everything is inside <doc... tags.

Best Answer

Related Solutions

Text Processing – Sort but Keep Header Line at the Top

Find a specific string and delete the whole structure

Related Question