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Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort. In other words, there is probably no significant market for optimizing shells. If you have half a million euro to spend on such research, you'll easily find someone to do it.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one. However, there are many large generated shell scripts, and for good reasons (e.g. GNU autoconf generated configure scripts).

Regarding huge textual files, passing them to cat as a single argument is not good practice, and most sysadmins know that (when any shell script takes more than a minute to run, you begin considering optimizing it). For large gigabytes files, cat is never the good tool to process them.

Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort. In other words, there is probably no significant market for optimizing shells. If you have half a million euro to spend on such research, you'll easily find someone to do it, and I believe it would give worthwhile results.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one. However, there are many large generated shell scripts, and for good reasons (e.g. GNU autoconf generated configure scripts).

Regarding huge textual files, passing them to cat as a single argument is not good practice, and most sysadmins know that (when any shell script takes more than a minute to run, you begin considering optimizing it). For large gigabytes files, cat is never the good tool to process them.

Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one. However, there are many large generated shell scripts, and for good reasons (e.g. GNU autoconf generated configure scripts).

Regarding huge textual files, passing them to cat as a single argument is not good practice, and most sysadmins know that (when any shell script takes more than a minute to run, you begin considering optimizing it). For large gigabytes files, cat is never the good tool to process them.

Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort. In other words, there is probably no significant market for optimizing shells. If you have half a million euro to spend on such research, you'll easily find someone to do it.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one. However, there are many large generated shell scripts, and for good reasons (e.g. GNU autoconf generated configure scripts).

Regarding huge textual files, passing them to cat as a single argument is not good practice, and most sysadmins know that (when any shell script takes more than a minute to run, you begin considering optimizing it). For large gigabytes files, cat is never the good tool to process them.

Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one.

Remember that a user could have a cat in his $PATH which is not exactly the POSIX cat (but perhaps some variant which could log something somewhere). In that case, you don't want the shell to remove it.

The PATH could change dynamically, and then cat is not what you believe it is. It would be quite difficult to write a shell doing the optimization you dream of.

Also, in practice, cat is a quite quick program. There are few practical reasons (except aesthetics) to avoid it.

See also the excellent Parsing POSIX [s]hell talk by Yann Regis-Gianas at FOSDEM2018. It gives other good reasons to avoid attempting doing what you dream of in a shell.

If performance was really an issue for shells, someone would have proposed a shell which uses sophisticated whole program compiler optimization, static source code analysis, and just-in-time compilation techniques (all these three domains have decades of progress and scientific publications and dedicated conferences, e.g. under SIGPLAN). Sadly, even as an interesting research topic, that is not currently funded by research agencies or venture capitalists, and I am deducing that it is simply not worth the effort.

On a practical side, rewriting, to improve its performance, a small (un hundred lines) shell script in any better scripting language (Python, AWK, Guile, ...) is commonly done. And it is not reasonable (for many software engineering reasons) to write large shell scripts: when you are writing a shell script exceeding a hundred lines, you do need to consider rewriting it (even for readability and maintenance reasons) in some more suitable language: as a programming language the shell is a very poor one. However, there are many large generated shell scripts, and for good reasons (e.g. GNU autoconf generated configure scripts).

Regarding huge textual files, passing them to cat as a single argument is not good practice, and most sysadmins know that (when any shell script takes more than a minute to run, you begin considering optimizing it). For large gigabytes files, cat is never the good tool to process them.