diff --git a/src/iomanip.cpp b/src/iomanip.cpp
index b29e367..40ef023 100644
--- a/src/iomanip.cpp
+++ b/src/iomanip.cpp
@@ -1,10 +1,14 @@
 #include "iomanip.hpp"
+#include <unistd.h>
+
+using namespace sc::io;
 
 static std::ostream& gray(std::ostream& out, int val, int code) {
     if (val < 0 || val > 23) {
         throw std::invalid_argument("gray value out of range");
     }
-    out << "\x1b[" << code << ";5;" << 232 + val << "m";
+    if (isatty_ostream(out))
+        out << "\x1b[" << code << ";5;" << 232 + val << "m";
     return out;
 }
 
@@ -12,152 +16,187 @@ static std::ostream& rgb(std::ostream& out, int r, int g, int b, int code) {
     if (r < 0 || r > 5 || g < 0 || g > 5 || b < 0 || b > 5) {
         throw std::invalid_argument("rgb color component out of range");
     }
-    out << "\x1b[" << code << ";5;" << (16 + 36 * r + 6 * g + b) << "m";
+    if (isatty_ostream(out))
+        out << "\x1b[" << code << ";5;" << (16 + 36 * r + 6 * g + b) << "m";
     return out;
 }
 
+bool sc::io::isatty_ostream(const std::ostream& out) {
+    return (&out == &std::cout && isatty(STDOUT_FILENO)) ||
+        (&out == &std::cerr && isatty(STDERR_FILENO));
+}
+
 std::ostream& sc::io::hide_cursor(std::ostream& out) {
-    out << "\x1b[?25l";
+    if (isatty_ostream(out))
+        out << "\x1b[?25l";
     return out;
 }
 
 std::ostream& sc::io::show_cursor(std::ostream& out) {
-    out << "\x1b[?25h";
+    if (isatty_ostream(out))
+        out << "\x1b[?25h";
     return out;
 }
 
 std::ostream& sc::io::reset(std::ostream& out) {
-    out << "\x1b[m";
+    if (isatty_ostream(out))
+        out << "\x1b[m";
     return out;
 }
 
 std::ostream& sc::io::bold(std::ostream& out) {
-    out << "\x1b[1m";
+    if (isatty_ostream(out))
+        out << "\x1b[1m";
     return out;
 }
 
 std::ostream& sc::io::italic(std::ostream& out) {
-    out << "\x1b[3m";
+    if (isatty_ostream(out))
+        out << "\x1b[3m";
     return out;
 }
 
 std::ostream& sc::io::underline(std::ostream& out) {
-    out << "\x1b[4m";
+    if (isatty_ostream(out))
+        out << "\x1b[4m";
     return out;
 }
 
 std::ostream& sc::io::overline(std::ostream& out) {
-    out << "\x1b[53m";
+    if (isatty_ostream(out))
+        out << "\x1b[53m";
     return out;
 }
 
 std::ostream& sc::io::strikethru(std::ostream& out) {
-    out << "\x1b[9m";
+    if (isatty_ostream(out))
+        out << "\x1b[9m";
     return out;
 }
 
 std::ostream& sc::io::blinkslow(std::ostream& out) {
-    out << "\x1b[5m";
+    if (isatty_ostream(out))
+        out << "\x1b[5m";
     return out;
 }
 
 std::ostream& sc::io::blinkfast(std::ostream& out) {
-    out << "\x1b[6m";
+    if (isatty_ostream(out))
+        out << "\x1b[6m";
     return out;
 }
 
 std::ostream& sc::io::reverse(std::ostream& out) {
-    out << "\x1b[7m";
+    if (isatty_ostream(out))
+        out << "\x1b[7m";
     return out;
 }
 
 std::ostream& sc::io::blackf(std::ostream& out) {
-    out << "\x1b[30m";
+    if (isatty_ostream(out))
+        out << "\x1b[30m";
     return out;
 }
 
 std::ostream& sc::io::redf(std::ostream& out) {
-    out << "\x1b[31m";
+    if (isatty_ostream(out))
+        out << "\x1b[31m";
     return out;
 }
 
 std::ostream& sc::io::greenf(std::ostream& out) {
-    out << "\x1b[32m";
+    if (isatty_ostream(out))
+        out << "\x1b[32m";
     return out;
 }
 
 std::ostream& sc::io::yellowf(std::ostream& out) {
-    out << "\x1b[33m";
+    if (isatty_ostream(out))
+        out << "\x1b[33m";
     return out;
 }
 
 std::ostream& sc::io::bluef(std::ostream& out) {
-    out << "\x1b[34m";
+    if (isatty_ostream(out))
+        out << "\x1b[34m";
     return out;
 }
 
 std::ostream& sc::io::magentaf(std::ostream& out) {
-    out << "\x1b[35m";
+    if (isatty_ostream(out))
+        out << "\x1b[35m";
     return out;
 }
 
 std::ostream& sc::io::cyanf(std::ostream& out) {
-    out << "\x1b[36m";
+    if (isatty_ostream(out))
+        out << "\x1b[36m";
     return out;
 }
 
 std::ostream& sc::io::whitef(std::ostream& out) {
-    out << "\x1b[37m";
+    if (isatty_ostream(out))
+        out << "\x1b[37m";
     return out;
 }
 
 std::ostream& sc::io::defaultf(std::ostream& out) {
-    out << "\x1b[39m";
+    if (isatty_ostream(out))
+        out << "\x1b[39m";
     return out;
 }
 
 std::ostream& sc::io::blackb(std::ostream& out) {
-    out << "\x1b[40m";
+    if (isatty_ostream(out))
+        out << "\x1b[40m";
     return out;
 }
 
 std::ostream& sc::io::redb(std::ostream& out) {
-    out << "\x1b[41m";
+    if (isatty_ostream(out))
+        out << "\x1b[41m";
     return out;
 }
 
 std::ostream& sc::io::greenb(std::ostream& out) {
-    out << "\x1b[42m";
+    if (isatty_ostream(out))
+        out << "\x1b[42m";
     return out;
 }
 
 std::ostream& sc::io::yellowb(std::ostream& out) {
-    out << "\x1b[43m";
+    if (isatty_ostream(out))
+        out << "\x1b[43m";
     return out;
 }
 
 std::ostream& sc::io::blueb(std::ostream& out) {
-    out << "\x1b[44m";
+    if (isatty_ostream(out))
+        out << "\x1b[44m";
     return out;
 }
 
 std::ostream& sc::io::magentab(std::ostream& out) {
-    out << "\x1b[45m";
+    if (isatty_ostream(out))
+        out << "\x1b[45m";
     return out;
 }
 
 std::ostream& sc::io::cyanb(std::ostream& out) {
-    out << "\x1b[46m";
+    if (isatty_ostream(out))
+        out << "\x1b[46m";
     return out;
 }
 
 std::ostream& sc::io::whiteb(std::ostream& out) {
-    out << "\x1b[47m";
+    if (isatty_ostream(out))
+        out << "\x1b[47m";
     return out;
 }
 
 std::ostream& sc::io::defaultb(std::ostream& out) {
-    out << "\x1b[49m";
+    if (isatty_ostream(out))
+        out << "\x1b[49m";
     return out;
 }
 
diff --git a/src/iomanip.hpp b/src/iomanip.hpp
index b161d68..5096c66 100644
--- a/src/iomanip.hpp
+++ b/src/iomanip.hpp
@@ -5,6 +5,8 @@
 
 namespace sc {
     namespace io {
+        bool isatty_ostream(const std::ostream& out);
+
         std::ostream& hide_cursor(std::ostream& out);
         std::ostream& show_cursor(std::ostream& out);
 
diff --git a/src/utils.cpp b/src/utils.cpp
index 014dcbb..9f98318 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -11,7 +11,8 @@
 using namespace sc;
 
 term::term(int fd) {
-    if (isatty(fd)) {
+    _isatty = isatty(fd);
+    if (_isatty) {
         throw_if_min1(ioctl(fd, TIOCGWINSZ, &_ws));
     }
     switch (fd) {
@@ -22,11 +23,11 @@ term::term(int fd) {
 }
 
 int term::rows() const {
-    return _ws.ws_row;
+    return _isatty ? _ws.ws_row : 0;
 }
 
 int term::cols() const {
-    return _ws.ws_col;
+    return _isatty ? _ws.ws_col : 0;
 }
 
 void term::progress(int prefixlen,
@@ -34,6 +35,8 @@ void term::progress(int prefixlen,
                     double cur,
                     double total) const
 {
+    if (!_isatty) return;
+
     // use unicode to make nice bar
     const char* bar[8] = {
         u8"\u258F", u8"\u258E", u8"\u258D", u8"\u258C",
diff --git a/src/utils.hpp b/src/utils.hpp
index 9f84843..ee58410 100644
--- a/src/utils.hpp
+++ b/src/utils.hpp
@@ -12,6 +12,7 @@ namespace sc {
     class term {
         struct winsize _ws;
         std::ostream* _out {nullptr};
+        bool _isatty {true};
 
         public:
             term(int fd);