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To count several characters, e.g. a , b and c , use egrep : egrep -o 'a|b|c' <file> | wc -l . Also, beware to NOT use wc -c as in the tr answer : since grep outputs line by line, wc would count end-of-lines as characters (hence doubling the number of characters).
The most easiest way to count the number of lines, words, and characters in text file is to use the Linux command “wc” in terminal. The command “wc” basically means “word count” and with different optional parameters one can use it to count the number of lines, words, and characters in a text file.
Cat(concatenate) command is very frequently used in Linux. It reads data from the file and gives their content as output. It helps us to create, view, concatenate files.
wc -c : Displays the count of bytes in a file. wc -m : prints the count of characters from a file. wc -L : prints only the length of the longest line in a file.
head works too:
head -c 100 file # returns the first 100 bytes in the file
..will extract the first 100 bytes and return them.
What's nice about using head for this is that the syntax for tail matches:
tail -c 100 file # returns the last 100 bytes in the file
You can combine these to get ranges of bytes. For example, to get the second 100 bytes from a file, read the first 200 with head and use tail to get the last 100:
head -c 200 file | tail -c 100
You can use dd to extract arbitrary chunks of bytes.
For example,
dd skip=1234 count=5 bs=1
would copy bytes 1235 to 1239 from its input to its output, and discard the rest.
To just get the first five bytes from standard input, do:
dd count=5 bs=1
Note that, if you want to specify the input file name, dd has old-fashioned argument parsing, so you would do:
dd count=5 bs=1 if=filename
Note also that dd verbosely announces what it did, so to toss that away, do:
dd count=5 bs=1 2>&-
or
dd count=5 bs=1 2>/dev/null
head:
head - output the first part of files
head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-c, --bytes=[-]N
print the first N bytes of each file; with the leading '-', print all but the last N bytes of each file
head or tail can do it as well:
head -c X
Prints the first X bytes (not necessarily characters if it's a UTF-16 file) of the file. tail will do the same, except for the last X bytes.
This (and cut) are portable.
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