Seq (Unix)

In its most basic use case, seq N prints out all the integers from 1 to N in sequence. This was convenient as the Unix shell at the time, the Bourne shell had no primitives for iterating over numbers, and its "for" command could only iterate over a list of words. seq was therefore used to generate such a list, as in this example:

# Remove file1 through file17:
for n in `seq 17`
do
    rm "file$n"
done

seq had additional options for controlling the start (not just end) of the numeric sequence, its increment (a floating point number), and the formatting of the number. GNU seq changed the name and meaning of the format option (from -p to -f) and added an option to control the separator between the numbers (-s, defaults to a newline).

With other alternatives available (e.g., expr), and with more recent shells adding builtin numeric iteration, seq is less commonly used today. In the modern Linux shell, bash, the above example can be alternatively written as:

for n in {1..17}
do
    rm "file$n"
done

and more efficiently, without actually generating the whole sequence in advance, as

for ((n=1; n<=17; n++))
do
    rm "file$n"
done

• seq(1) – Linux User Commands Manual
• seq(1) – Plan 9 Programmer's Manual, Volume 1