5 ms·

I build pipes left to right, and I read pipes left to right... 1 -> 2 -> 3 is easier that (2 <- 1) -> 3

samsquire 3y ago
You can put shell file redirections such as "< file" at the beginning of the line. In bash, type: < /etc/resolv.conf grep nameserver (That < is not a prompt, that's the less than symbol)
- tolciho 3y ago
  Sometimes you can prefix with "< file". Sometimes, not so much. < /etc/passwd while IFS= read line || [ -n "$line" ]; do printf '%s\n' "$line"; done Meanwhile, in ZSH... Meanwhile, in languages that do not need IFS= and || [ -n "$line" ] checks...
- kzrdude 3y ago
  Nice, I learned something and thank you
- ilyt 3y ago
  aliasing c to cat still requires less keystrokes
- antonvs 3y ago
  But in a multi-step pipe, that’s still asymmetric and to me, less natural as a result. cat f | grep nameserver | otherproc… …is more consistently compositional.
throwaway173738 3y ago
This is also the classic argument against reverse polish notation. Operator-first makes it harder to say the name of an operator in a sentence.
- ajuc 3y ago
  Reverse polish notation is operator last.
  - eru 3y ago
    Operator first makes the sentence easier: '+ 2 3' becomes 'add 2 and 3' In any case, it's a silly objection.
    - pxc 3y ago
      It's an especially silly objection in the case of the command line, where prefix notation is already the norm anyway. + 2 3 is naturally how you'd write addition if addition were a standalone Unix command!
- jrockway 3y ago
  Infix operators are very weird, though. They come from math, where every elementary school student has to memorize "please excuse my dear aunt sally" to be able to answer a simple question like "what is 2³ + 4 ÷ 2". C copied this concept, and nobody really ever bothered to memorize C's operator precedence, so they just end up writing Lisp but with the operators in the middle. pow(2, 3) + (4/2). Note that some operators appear prefix instead of infix for no apparent reason. (You can't just remember what you learned in math class when writing a computer program, because now we have bitwise and, or, xor, left shift, right shift, equality, pointer dereferencing, assignment, logical and, or, modulo, pre-increment, post-increment, bitwise not, logical not, etc. So you have to learn it all again. And it's different for every language.) Put everything up front, and suddenly you don't have to think about this anymore. (+ (expt 2 3) (/ 4 2)). The computer just does what you say and there are no rules to memorize. Personally, I always use RPN calculators (dc is my favorite), because I don't trust the calculator to remember operator precedence. They usually do it right, but it's difficult to reason about. (The example would be "2 3 ^ 4 2 / + p" in dc.)
  - vram22 3y ago
    >every elementary school student has to memorize "please excuse my dear aunt sally" In Indian schools it used to be BODMAS, for Brackets Of Division Multiplication Addition Subtraction, for operator precedence, for which our teachers told us the mnemonic was badmaash, meaning a scoundrel or a villain, in Hindi. Guaranteed to make kids remember it. :) Of, as in half or a quarter or ... of some other number.

You can put shell file redirections such as "< file" at the beginning of the line. In bash, type: < /etc/resolv.conf grep nameserver (That < is not a prompt, that's the less than symbol)

tolciho 3y ago
Sometimes you can prefix with "< file". Sometimes, not so much. < /etc/passwd while IFS= read line || [ -n "$line" ]; do printf '%s\n' "$line"; done Meanwhile, in ZSH... Meanwhile, in languages that do not need IFS= and || [ -n "$line" ] checks...
kzrdude 3y ago
Nice, I learned something and thank you
ilyt 3y ago
aliasing c to cat still requires less keystrokes
antonvs 3y ago
But in a multi-step pipe, that’s still asymmetric and to me, less natural as a result. cat f | grep nameserver | otherproc… …is more consistently compositional.

throwaway173738 3y ago

This is also the classic argument against reverse polish notation. Operator-first makes it harder to say the name of an operator in a sentence.

ajuc 3y ago
Reverse polish notation is operator last.
- eru 3y ago
  Operator first makes the sentence easier: '+ 2 3' becomes 'add 2 and 3' In any case, it's a silly objection.
  - pxc 3y ago
    It's an especially silly objection in the case of the command line, where prefix notation is already the norm anyway. + 2 3 is naturally how you'd write addition if addition were a standalone Unix command!
jrockway 3y ago
Infix operators are very weird, though. They come from math, where every elementary school student has to memorize "please excuse my dear aunt sally" to be able to answer a simple question like "what is 2³ + 4 ÷ 2". C copied this concept, and nobody really ever bothered to memorize C's operator precedence, so they just end up writing Lisp but with the operators in the middle. pow(2, 3) + (4/2). Note that some operators appear prefix instead of infix for no apparent reason. (You can't just remember what you learned in math class when writing a computer program, because now we have bitwise and, or, xor, left shift, right shift, equality, pointer dereferencing, assignment, logical and, or, modulo, pre-increment, post-increment, bitwise not, logical not, etc. So you have to learn it all again. And it's different for every language.) Put everything up front, and suddenly you don't have to think about this anymore. (+ (expt 2 3) (/ 4 2)). The computer just does what you say and there are no rules to memorize. Personally, I always use RPN calculators (dc is my favorite), because I don't trust the calculator to remember operator precedence. They usually do it right, but it's difficult to reason about. (The example would be "2 3 ^ 4 2 / + p" in dc.)
- vram22 3y ago
  >every elementary school student has to memorize "please excuse my dear aunt sally" In Indian schools it used to be BODMAS, for Brackets Of Division Multiplication Addition Subtraction, for operator precedence, for which our teachers told us the mnemonic was badmaash, meaning a scoundrel or a villain, in Hindi. Guaranteed to make kids remember it. :) Of, as in half or a quarter or ... of some other number.